# EDGAR Filing Document

**Accession Number:** 0000002110
**File Stem:** 0001193125-26-096296
**Filing Date:** 2026-3
**Character Count:** 679784
**Document Hash:** b4376765c3598d11540fb2406af51f9e
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-096296.hdr.sgml**: 20260306

**ACCESSION NUMBER**: 0001193125-26-096296

**CONFORMED SUBMISSION TYPE**: N-CSR

**PUBLIC DOCUMENT COUNT**: 45

**CONFORMED PERIOD OF REPORT**: 20251231

**FILED AS OF DATE**: 20260306

**DATE AS OF CHANGE**: 20260306

**EFFECTIVENESS DATE**: 20260306

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** COLUMBIA ACORN TRUST
- **CENTRAL INDEX KEY:** 0000002110

**ORGANIZATION NAME:**
- **EIN:** 362692100
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** N-CSR
- **SEC ACT:** 1940 Act
- **SEC FILE NUMBER:** 811-01829
- **FILM NUMBER:** 26730485

**BUSINESS ADDRESS:**
- **STREET 1:** 71 S. WACKER DRIVE, SUITE 2500
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606
- **BUSINESS PHONE:** 3126349200

**MAIL ADDRESS:**
- **STREET 1:** 71 S. WACKER DRIVE, SUITE 2500
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** LIBERTY ACORN TRUST
- **DATE OF NAME CHANGE:** 20010424

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ACORN INVESTMENT TRUST
- **DATE OF NAME CHANGE:** 19940204

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ACORN FUND INC
- **DATE OF NAME CHANGE:** 19920703

## Series and Classes Contracts Data

### Columbia Acorn Fund (Series ID: S000009184)

| Class ID   | Class Name                                | Ticker Symbol   |
|:---|:---|:---|
| C000024954 | Columbia Acorn Fund Class A               | LACAX           |
| C000024956 | Columbia Acorn Fund Class C               | LIACX           |
| C000024957 | Columbia Acorn Fund Institutional Class   | ACRNX           |
| C000122736 | Columbia Acorn Fund Institutional 2 Class | CRBRX           |
| C000122737 | Columbia Acorn Fund Institutional 3 Class | CRBYX           |
| C000251059 | Columbia Acorn Fund Class S               | ACRSX           |

### Columbia Acorn International (Series ID: S000009185)

| Class ID   | Class Name                                         | Ticker Symbol   |
|:---|:---|:---|
| C000024958 | Columbia Acorn International Class A               | LAIAX           |
| C000024961 | Columbia Acorn International Institutional Class   | ACINX           |
| C000097733 | Columbia Acorn International Institutional 2 Class | CAIRX           |
| C000122739 | Columbia Acorn International Institutional 3 Class | CCYIX           |
| C000251060 | Columbia Acorn International Class S               | CCIDX           |

### Columbia Acorn International Select (Series ID: S000009188)

| Class ID   | Class Name                                                | Ticker Symbol   |
|:---|:---|:---|
| C000024970 | Columbia Acorn International Select Class A               | LAFAX           |
| C000024973 | Columbia Acorn International Select Institutional Class   | ACFFX           |
| C000122746 | Columbia Acorn International Select Institutional 2 Class | CRIRX           |
| C000122747 | Columbia Acorn International Select Institutional 3 Class | CSIRX           |
| C000251061 | Columbia Acorn International Select Class S               | ACFEX           |

### Columbia Thermostat Fund (Series ID: S000009189)

| Class ID   | Class Name                                     | Ticker Symbol   |
|:---|:---|:---|
| C000024974 | Columbia Thermostat Fund Class A               | CTFAX           |
| C000024976 | Columbia Thermostat Fund Class C               | CTFDX           |
| C000024977 | Columbia Thermostat Fund Institutional Class   | COTZX           |
| C000122750 | Columbia Thermostat Fund Institutional 2 Class | CQTRX           |
| C000122751 | Columbia Thermostat Fund Institutional 3 Class | CYYYX           |
| C000251062 | Columbia Thermostat Class S                    | COTDX           |

### Columbia Acorn European Fund (Series ID: S000033621)

| Class ID   | Class Name                                       | Ticker Symbol   |
|:---|:---|:---|
| C000103324 | Columbia Acorn European Fund Class A             | CAEAX           |
| C000103327 | Columbia Acorn European Fund Institutional Class | CAEZX           |

?xml version='1.0' encoding='ASCII'? N-CSR

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

### FORM N-CSR

#### CERTIFIED SHAREHOLDER REPORT OF REGISTERED

#### MANAGEMENT INVESTMENT COMPANIES

#### Investment Company Act file number 811-01829

## Columbia Acorn Trust

#### (Exact name of registrant as specified in charter)

#### 290 Congress Street

#### Boston, MA 02210

#### (Address of principal executive offices) (Zip code)

#### Michael G. Clarke

#### c/o Columbia Management Investment Advisers, LLC

#### 290 Congress Street

#### Boston, MA 02210

#### Ryan C. Larrenaga, Esq.

#### c/o Columbia Management Investment Advisers, LLC

#### 290 Congress Street

#### Boston, MA 02210

#### (Name and address of agent for service)

#### Registrant's telephone number, including area code: (800) 345-6611

#### Date of fiscal year end: Last Day of December

#### Date of reporting period: December 31, 2025

------

#### Item 1. Reports to Stockholders.

# Columbia Acorn European Fund℠
Class A \| CAEAX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn European Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class A | $150 | 1.34% |

---

## Management's Discussion of Fund Performance
The performance of Class A shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and health care sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A larger allocation to the financials sector and smaller allocations to the consumer discretionary, information technology, communication services and consumer staples sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in RENK Group, a German aerospace and defense company; National Bank of Greece, a Greek diversified financial services company; flatexDEGIRO, a German brokerage platform; Banco Comercial Portugues, a Portuguese bank and financial services company; and Allfunds Group, a London-based financial services provider, were among the top contributors to Fund performance.

### Top Performance Detractors
**Stock selection** \| Selections in the materials, consumer discretionary, communication services, industrials and information technology sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A larger weighting in the materials sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Munters Group, a Swedish supplier of air treatment solutions; R&S Group Holding, a Swiss power component manufacturer; Azelis Group, a Belgium-based company engaged in specialty chemicals and food ingredients; Interparfums, Inc., a perfume and fragrance manufacturer; and Breedon Group, a UK-based cement, asphalt and concrete supplier, were top detractors from the Fund's performance during the period.

Columbia Acorn European Fund℠ \| Class A **\|** ASR109_01_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g59j64.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn European Fund℠ Class A (including sales charges) ($20265)** | **MSCI ACWI ex USA Index (Net) ($22432)** | **MSCI AC Europe Small Cap Index (Net) ($20167)** |
| **12/15** | $9425 | $10000 | $10000 |
| **01/16** | $8863 | $9320 | $9150 |
| **02/16** | $8780 | $9213 | $9143 |
| **03/16** | $9527 | $9962 | $9913 |
| **04/16** | $9534 | $10225 | $10044 |
| **05/16** | $9681 | $10052 | $10157 |
| **06/16** | $9063 | $9898 | $9248 |
| **07/16** | $9608 | $10388 | $9819 |
| **08/16** | $9672 | $10453 | $9938 |
| **09/16** | $9838 | $10582 | $10130 |
| **10/16** | $9223 | $10430 | $9643 |
| **11/16** | $8878 | $10189 | $9437 |
| **12/16** | $9098 | $10450 | $9843 |
| **01/17** | $9478 | $10820 | $10182 |
| **02/17** | $9678 | $10992 | $10338 |
| **03/17** | $9968 | $11271 | $10681 |
| **04/17** | $10728 | $11512 | $11396 |
| **05/17** | $11366 | $11886 | $11887 |
| **06/17** | $11236 | $11923 | $11773 |
| **07/17** | $11604 | $12362 | $12303 |
| **08/17** | $11598 | $12427 | $12338 |
| **09/17** | $12011 | $12657 | $12805 |
| **10/17** | $12173 | $12896 | $12876 |
| **11/17** | $12315 | $13000 | $12923 |
| **12/17** | $12545 | $13291 | $13337 |
| **01/18** | $13274 | $14031 | $14109 |
| **02/18** | $12747 | $13370 | $13416 |
| **03/18** | $12552 | $13134 | $13293 |
| **04/18** | $12734 | $13343 | $13577 |
| **05/18** | $12910 | $13035 | $13320 |
| **06/18** | $12619 | $12790 | $13165 |
| **07/18** | $12907 | $13096 | $13365 |
| **08/18** | $13032 | $12822 | $13195 |
| **09/18** | $12600 | $12881 | $12932 |
| **10/18** | $11283 | $11833 | $11664 |
| **11/18** | $10897 | $11945 | $11274 |
| **12/18** | $10190 | $11404 | $10657 |
| **01/19** | $11251 | $12266 | $11658 |
| **02/19** | $11722 | $12506 | $11963 |
| **03/19** | $11860 | $12580 | $11942 |
| **04/19** | $12639 | $12912 | $12465 |
| **05/19** | $12239 | $12219 | $11684 |
| **06/19** | $13202 | $12955 | $12298 |
| **07/19** | $12698 | $12798 | $12017 |
| **08/19** | $12384 | $12403 | $11678 |
| **09/19** | $12547 | $12722 | $11964 |
| **10/19** | $13313 | $13166 | $12538 |
| **11/19** | $14178 | $13282 | $12960 |
| **12/19** | $14873 | $13857 | $13751 |
| **01/20** | $14404 | $13485 | $13355 |
| **02/20** | $13229 | $12419 | $12152 |
| **03/20** | $10653 | $10621 | $9557 |
| **04/20** | $12112 | $11426 | $10628 |
| **05/20** | $13671 | $11800 | $11352 |
| **06/20** | $13906 | $12333 | $11631 |
| **07/20** | $15201 | $12883 | $12369 |
| **08/20** | $16231 | $13434 | $13201 |
| **09/20** | $15899 | $13104 | $12864 |
| **10/20** | $15208 | $12822 | $12202 |
| **11/20** | $16889 | $14547 | $14456 |
| **12/20** | $18264 | $15333 | $15690 |
| **01/21** | $18304 | $15367 | $15660 |
| **02/21** | $18370 | $15671 | $16261 |
| **03/21** | $18164 | $15869 | $16526 |
| **04/21** | $19766 | $16336 | $17557 |
| **05/21** | $20310 | $16847 | $18198 |
| **06/21** | $20350 | $16738 | $17548 |
| **07/21** | $21573 | $16462 | $18180 |
| **08/21** | $22423 | $16775 | $18739 |
| **09/21** | $20775 | $16238 | $17582 |
| **10/21** | $21925 | $16626 | $18186 |
| **11/21** | $21254 | $15877 | $17091 |
| **12/21** | $22185 | $16533 | $18003 |
| **01/22** | $18797 | $15924 | $16586 |
| **02/22** | $17652 | $15609 | $15901 |
| **03/22** | $17333 | $15634 | $15841 |
| **04/22** | $15728 | $14652 | $14758 |
| **05/22** | $15382 | $14757 | $14732 |
| **06/22** | $13499 | $13488 | $12701 |
| **07/22** | $15189 | $13949 | $13587 |
| **08/22** | $13525 | $13501 | $12505 |
| **09/22** | $11542 | $12152 | $10867 |
| **10/22** | $12467 | $12515 | $11752 |
| **11/22** | $14151 | $13992 | $13050 |
| **12/22** | $13718 | $13887 | $13217 |
| **01/23** | $14850 | $15014 | $14412 |
| **02/23** | $14896 | $14487 | $14467 |
| **03/23** | $15449 | $14841 | $14190 |
| **04/23** | $16008 | $15099 | $14648 |
| **05/23** | $15815 | $14550 | $13808 |
| **06/23** | $15981 | $15203 | $14239 |
| **07/23** | $16314 | $15821 | $14925 |
| **08/23** | $15329 | $15106 | $14311 |
| **09/23** | $14131 | $14629 | $13551 |
| **10/23** | $13186 | $14025 | $12741 |
| **11/23** | $15416 | $15288 | $14281 |
| **12/23** | $17115 | $16056 | $15403 |
| **01/24** | $16458 | $15897 | $15059 |
| **02/24** | $16954 | $16299 | $15048 |
| **03/24** | $17269 | $16808 | $15603 |
| **04/24** | $16231 | $16507 | $15356 |
| **05/24** | $17497 | $16986 | $16468 |
| **06/24** | $16936 | $16970 | $15750 |
| **07/24** | $18064 | $17363 | $16542 |
| **08/24** | $18605 | $17857 | $16825 |
| **09/24** | $18706 | $18338 | $17032 |
| **10/24** | $17328 | $17438 | $15825 |
| **11/24** | $16990 | $17280 | $15625 |
| **12/24** | $16363 | $16945 | $15297 |
| **01/25** | $17076 | $17627 | $15953 |
| **02/25** | $17028 | $17872 | $16042 |
| **03/25** | $16548 | $17831 | $16172 |
| **04/25** | $17405 | $18475 | $17276 |
| **05/25** | $19064 | $19322 | $18430 |
| **06/25** | $19859 | $19977 | $19246 |
| **07/25** | $19674 | $19920 | $19009 |
| **08/25** | $19934 | $20611 | $19333 |
| **09/25** | $20147 | $21354 | $19460 |
| **10/25** | $19674 | $21785 | $19351 |
| **11/25** | $19797 | $21780 | $19446 |
| **12/25** | $20265 | $22432 | $20167 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class A (excluding sales charges) | 23.85 | 2.10 | 7.96 |
| Class A (including sales charges) | 16.71 | 0.90 | 7.32 |
| MSCI ACWI ex USA Index (Net) | 32.39 | 7.91 | 8.41 |
| MSCI AC Europe Small Cap Index (Net) | 31.83 | 5.15 | 7.27 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $36672374 |
| **Total number of portfolio holdings** | 87 |
| **Management services fees (represents 1.00% of Fund average net assets)** | $395935 |
| **Portfolio turnover for the reporting period** | 82% |

---

Columbia Acorn European Fund℠ \| Class A **\|** ASR109_01_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| United Kingdom | 30.1% |
| France | 13.3% |
| Germany | 9.4% |
| Italy | 6.4% |
| Ireland | 5.4% |
| Austria | 4.9% |
| Switzerland | 4.6% |
| Greece | 3.8% |
| Spain | 3.5% |
| Sweden | 3.1% |
| Other | 14.1% |

---

### Top Holdings

---

| | |
|:---|:---|
| Elis SA | 3.0% |
| flatexDEGIRO AG | 2.7% |
| Nexans SA | 2.6% |
| SPIE SA | 2.2% |
| DO & CO AG | 2.2% |
| CVS Group PLC | 2.1% |
| CTP NV | 2.0% |
| Safestore Holdings PLC | 2.0% |
| Bilfinger SE | 1.9% |
| Quilter PLC | 1.9% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 30.1% |
| Financials | 23.8% |
| Real Estate | 8.6% |
| Materials | 8.5% |
| Health Care | 8.0% |
| Consumer Discretionary | 5.4% |
| Consumer Staples | 3.5% |
| Utilities | 2.7% |
| Energy | 2.7% |
| Information Technology | 2.7% |
| Other | 1.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn European Fund℠ \| Class A **\|** ASR109_01_(02/26) \|

# Columbia Acorn European Fund℠
Institutional Class \| CAEZX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn European Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional Class | $123 | 1.10% |

---

## Management's Discussion of Fund Performance
The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and health care sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A larger allocation to the financials sector and smaller allocations to the consumer discretionary, information technology, communication services and consumer staples sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in RENK Group, a German aerospace and defense company; National Bank of Greece, a Greek diversified financial services company; flatexDEGIRO, a German brokerage platform; Banco Comercial Portugues, a Portuguese bank and financial services company; and Allfunds Group, a London-based financial services provider, were among the top contributors to Fund performance.

### Top Performance Detractors
**Stock selection** \| Selections in the materials, consumer discretionary, communication services, industrials and information technology sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A larger weighting in the materials sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Munters Group, a Swedish supplier of air treatment solutions; R&S Group Holding, a Swiss power component manufacturer; Azelis Group, a Belgium-based company engaged in specialty chemicals and food ingredients; Interparfums, Inc., a perfume and fragrance manufacturer; and Breedon Group, a UK-based cement, asphalt and concrete supplier, were top detractors from the Fund's performance during the period.

Columbia Acorn European Fund℠ \| Institutional Class **\|** ASR109_08_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g47v82.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn European Fund℠ Institutional Class ($22048)** | **MSCI ACWI ex USA Index (Net) ($22432)** | **MSCI AC Europe Small Cap Index (Net) ($20167)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9403 | $9320 | $9150 |
| **02/16** | $9322 | $9213 | $9143 |
| **03/16** | $10115 | $9962 | $9913 |
| **04/16** | $10122 | $10225 | $10044 |
| **05/16** | $10278 | $10052 | $10157 |
| **06/16** | $9630 | $9898 | $9248 |
| **07/16** | $10207 | $10388 | $9819 |
| **08/16** | $10275 | $10453 | $9938 |
| **09/16** | $10452 | $10582 | $10130 |
| **10/16** | $9807 | $10430 | $9643 |
| **11/16** | $9440 | $10189 | $9437 |
| **12/16** | $9671 | $10450 | $9843 |
| **01/17** | $10082 | $10820 | $10182 |
| **02/17** | $10302 | $10992 | $10338 |
| **03/17** | $10610 | $11271 | $10681 |
| **04/17** | $11426 | $11512 | $11396 |
| **05/17** | $12104 | $11886 | $11887 |
| **06/17** | $11973 | $11923 | $11773 |
| **07/17** | $12365 | $12362 | $12303 |
| **08/17** | $12358 | $12427 | $12338 |
| **09/17** | $12798 | $12657 | $12805 |
| **10/17** | $12977 | $12896 | $12876 |
| **11/17** | $13128 | $13000 | $12923 |
| **12/17** | $13380 | $13291 | $13337 |
| **01/18** | $14157 | $14031 | $14109 |
| **02/18** | $13602 | $13370 | $13416 |
| **03/18** | $13394 | $13134 | $13293 |
| **04/18** | $13595 | $13343 | $13577 |
| **05/18** | $13782 | $13035 | $13320 |
| **06/18** | $13472 | $12790 | $13165 |
| **07/18** | $13787 | $13096 | $13365 |
| **08/18** | $13919 | $12822 | $13195 |
| **09/18** | $13458 | $12881 | $12932 |
| **10/18** | $12062 | $11833 | $11664 |
| **11/18** | $11650 | $11945 | $11274 |
| **12/18** | $10895 | $11404 | $10657 |
| **01/19** | $12034 | $12266 | $11658 |
| **02/19** | $12537 | $12506 | $11963 |
| **03/19** | $12690 | $12580 | $11942 |
| **04/19** | $13521 | $12912 | $12465 |
| **05/19** | $13095 | $12219 | $11684 |
| **06/19** | $14136 | $12955 | $12298 |
| **07/19** | $13598 | $12798 | $12017 |
| **08/19** | $13256 | $12403 | $11678 |
| **09/19** | $13437 | $12722 | $11964 |
| **10/19** | $14262 | $13166 | $12538 |
| **11/19** | $15191 | $13282 | $12960 |
| **12/19** | $15945 | $13857 | $13751 |
| **01/20** | $15444 | $13485 | $13355 |
| **02/20** | $14187 | $12419 | $12152 |
| **03/20** | $11427 | $10621 | $9557 |
| **04/20** | $12994 | $11426 | $10628 |
| **05/20** | $14667 | $11800 | $11352 |
| **06/20** | $14918 | $12333 | $11631 |
| **07/20** | $16317 | $12883 | $12369 |
| **08/20** | $17424 | $13434 | $13201 |
| **09/20** | $17069 | $13104 | $12864 |
| **10/20** | $16338 | $12822 | $12202 |
| **11/20** | $18142 | $14547 | $14456 |
| **12/20** | $19626 | $15333 | $15690 |
| **01/21** | $19675 | $15367 | $15660 |
| **02/21** | $19746 | $15671 | $16261 |
| **03/21** | $19533 | $15869 | $16526 |
| **04/21** | $21252 | $16336 | $17557 |
| **05/21** | $21841 | $16847 | $18198 |
| **06/21** | $21891 | $16738 | $17548 |
| **07/21** | $23211 | $16462 | $18180 |
| **08/21** | $24127 | $16775 | $18739 |
| **09/21** | $22359 | $16238 | $17582 |
| **10/21** | $23602 | $16626 | $18186 |
| **11/21** | $22885 | $15877 | $17091 |
| **12/21** | $23895 | $16533 | $18003 |
| **01/22** | $20251 | $15924 | $16586 |
| **02/22** | $19025 | $15609 | $15901 |
| **03/22** | $18675 | $15634 | $15841 |
| **04/22** | $16950 | $14652 | $14758 |
| **05/22** | $16586 | $14757 | $14732 |
| **06/22** | $14554 | $13488 | $12701 |
| **07/22** | $16387 | $13949 | $13587 |
| **08/22** | $14597 | $13501 | $12505 |
| **09/22** | $12457 | $12152 | $10867 |
| **10/22** | $13456 | $12515 | $11752 |
| **11/22** | $15274 | $13992 | $13050 |
| **12/22** | $14811 | $13887 | $13217 |
| **01/23** | $16037 | $15014 | $14412 |
| **02/23** | $16087 | $14487 | $14467 |
| **03/23** | $16693 | $14841 | $14190 |
| **04/23** | $17299 | $15099 | $14648 |
| **05/23** | $17092 | $14550 | $13808 |
| **06/23** | $17278 | $15203 | $14239 |
| **07/23** | $17634 | $15821 | $14925 |
| **08/23** | $16579 | $15106 | $14311 |
| **09/23** | $15288 | $14629 | $13551 |
| **10/23** | $14262 | $14025 | $12741 |
| **11/23** | $16679 | $15288 | $14281 |
| **12/23** | $18526 | $16056 | $15403 |
| **01/24** | $17822 | $15897 | $15059 |
| **02/24** | $18361 | $16299 | $15048 |
| **03/24** | $18699 | $16808 | $15603 |
| **04/24** | $17584 | $16507 | $15356 |
| **05/24** | $18958 | $16986 | $16468 |
| **06/24** | $18356 | $16970 | $15750 |
| **07/24** | $19582 | $17363 | $16542 |
| **08/24** | $20177 | $17857 | $16825 |
| **09/24** | $20286 | $18338 | $17032 |
| **10/24** | $18798 | $17438 | $15825 |
| **11/24** | $18436 | $17280 | $15625 |
| **12/24** | $17751 | $16945 | $15297 |
| **01/25** | $18533 | $17627 | $15953 |
| **02/25** | $18482 | $17872 | $16042 |
| **03/25** | $17973 | $17831 | $16172 |
| **04/25** | $18902 | $18475 | $17276 |
| **05/25** | $20710 | $19322 | $18430 |
| **06/25** | $21580 | $19977 | $19246 |
| **07/25** | $21374 | $19920 | $19009 |
| **08/25** | $21662 | $20611 | $19333 |
| **09/25** | $21905 | $21354 | $19460 |
| **10/25** | $21396 | $21785 | $19351 |
| **11/25** | $21529 | $21780 | $19446 |
| **12/25** | $22048 | $22432 | $20167 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional Class | 24.20 | 2.35 | 8.23 |
| MSCI ACWI ex USA Index (Net) | 32.39 | 7.91 | 8.41 |
| MSCI AC Europe Small Cap Index (Net) | 31.83 | 5.15 | 7.27 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $36672374 |
| **Total number of portfolio holdings** | 87 |
| **Management services fees (represents 1.00% of Fund average net assets)** | $395935 |
| **Portfolio turnover for the reporting period** | 82% |

---

Columbia Acorn European Fund℠ \| Institutional Class **\|** ASR109_08_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| United Kingdom | 30.1% |
| France | 13.3% |
| Germany | 9.4% |
| Italy | 6.4% |
| Ireland | 5.4% |
| Austria | 4.9% |
| Switzerland | 4.6% |
| Greece | 3.8% |
| Spain | 3.5% |
| Sweden | 3.1% |
| Other | 14.1% |

---

### Top Holdings

---

| | |
|:---|:---|
| Elis SA | 3.0% |
| flatexDEGIRO AG | 2.7% |
| Nexans SA | 2.6% |
| SPIE SA | 2.2% |
| DO & CO AG | 2.2% |
| CVS Group PLC | 2.1% |
| CTP NV | 2.0% |
| Safestore Holdings PLC | 2.0% |
| Bilfinger SE | 1.9% |
| Quilter PLC | 1.9% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 30.1% |
| Financials | 23.8% |
| Real Estate | 8.6% |
| Materials | 8.5% |
| Health Care | 8.0% |
| Consumer Discretionary | 5.4% |
| Consumer Staples | 3.5% |
| Utilities | 2.7% |
| Energy | 2.7% |
| Information Technology | 2.7% |
| Other | 1.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn European Fund℠ \| Institutional Class **\|** ASR109_08_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Class A \| LACAX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class A | $109 | 1.07% |

---

## Management's Discussion of Fund Performance
The performance of Class A shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Class A **\|** ASR110_01_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g12f26.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Class A (including sales charges) ($20858)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $9423 | $10000 | $10000 |
| **01/16** | $8557 | $9436 | $9011 |
| **02/16** | $8498 | $9433 | $9038 |
| **03/16** | $9161 | $10097 | $9734 |
| **04/16** | $9262 | $10159 | $9827 |
| **05/16** | $9535 | $10341 | $10071 |
| **06/16** | $9387 | $10362 | $9997 |
| **07/16** | $9906 | $10774 | $10591 |
| **08/16** | $9972 | $10801 | $10664 |
| **09/16** | $10021 | $10818 | $10695 |
| **10/16** | $9713 | $10584 | $10137 |
| **11/16** | $10346 | $11058 | $10876 |
| **12/16** | $10370 | $11274 | $10973 |
| **01/17** | $10619 | $11486 | $11233 |
| **02/17** | $10992 | $11913 | $11573 |
| **03/17** | $11062 | $11921 | $11659 |
| **04/17** | $11303 | $12047 | $11864 |
| **05/17** | $11419 | $12171 | $11869 |
| **06/17** | $11642 | $12280 | $12140 |
| **07/17** | $11699 | $12512 | $12301 |
| **08/17** | $11756 | $12536 | $12325 |
| **09/17** | $12232 | $12842 | $12841 |
| **10/17** | $12611 | $13122 | $13185 |
| **11/17** | $12967 | $13521 | $13619 |
| **12/17** | $12954 | $13656 | $13656 |
| **01/18** | $13696 | $14375 | $14338 |
| **02/18** | $13245 | $13846 | $13868 |
| **03/18** | $13415 | $13568 | $13981 |
| **04/18** | $13305 | $13619 | $13892 |
| **05/18** | $14147 | $14004 | $14631 |
| **06/18** | $14277 | $14095 | $14754 |
| **07/18** | $14612 | $14563 | $15030 |
| **08/18** | $15535 | $15074 | $16046 |
| **09/18** | $15305 | $15099 | $15811 |
| **10/18** | $13448 | $13988 | $13912 |
| **11/18** | $13836 | $14268 | $14175 |
| **12/18** | $12277 | $12940 | $12637 |
| **01/19** | $13546 | $14051 | $14141 |
| **02/19** | $14364 | $14545 | $15073 |
| **03/19** | $14295 | $14757 | $15036 |
| **04/19** | $14848 | $15346 | $15562 |
| **05/19** | $14030 | $14353 | $14528 |
| **06/19** | $14848 | $15361 | $15659 |
| **07/19** | $15140 | $15590 | $15903 |
| **08/19** | $14617 | $15272 | $15451 |
| **09/19** | $14288 | $15540 | $15161 |
| **10/19** | $14446 | $15874 | $15550 |
| **11/19** | $15347 | $16478 | $16609 |
| **12/19** | $15496 | $16954 | $16763 |
| **01/20** | $15456 | $16935 | $16781 |
| **02/20** | $14278 | $15549 | $15643 |
| **03/20** | $12188 | $13410 | $12871 |
| **04/20** | $13868 | $15187 | $14935 |
| **05/20** | $15469 | $15999 | $16494 |
| **06/20** | $15640 | $16364 | $17101 |
| **07/20** | $16512 | $17294 | $18037 |
| **08/20** | $16976 | $18546 | $18849 |
| **09/20** | $17089 | $17871 | $18704 |
| **10/20** | $17173 | $17485 | $18925 |
| **11/20** | $18973 | $19613 | $21682 |
| **12/20** | $20018 | $20495 | $23547 |
| **01/21** | $20349 | $20404 | $24205 |
| **02/21** | $21185 | $21042 | $24965 |
| **03/21** | $20397 | $21796 | $24133 |
| **04/21** | $21091 | $22919 | $24980 |
| **05/21** | $20255 | $23024 | $24286 |
| **06/21** | $21565 | $23592 | $25589 |
| **07/21** | $21814 | $23991 | $25035 |
| **08/21** | $22496 | $24675 | $25662 |
| **09/21** | $21216 | $23568 | $24685 |
| **10/21** | $22928 | $25161 | $25951 |
| **11/21** | $22047 | $24778 | $24614 |
| **12/21** | $21778 | $25754 | $24735 |
| **01/22** | $18319 | $24239 | $21471 |
| **02/22** | $18275 | $23628 | $21536 |
| **03/22** | $17949 | $24395 | $21691 |
| **04/22** | $15425 | $22206 | $19214 |
| **05/22** | $14838 | $22176 | $18748 |
| **06/22** | $13719 | $20321 | $17450 |
| **07/22** | $15795 | $22227 | $19441 |
| **08/22** | $15352 | $21397 | $19072 |
| **09/22** | $13882 | $19413 | $17429 |
| **10/22** | $14815 | $21005 | $18846 |
| **11/22** | $15235 | $22102 | $19406 |
| **12/22** | $14372 | $20808 | $18251 |
| **01/23** | $15795 | $22241 | $20078 |
| **02/23** | $15749 | $21721 | $19761 |
| **03/23** | $15819 | $22302 | $19446 |
| **04/23** | $15632 | $22539 | $19200 |
| **05/23** | $15492 | $22627 | $19179 |
| **06/23** | $16682 | $24172 | $20693 |
| **07/23** | $17195 | $25039 | $21384 |
| **08/23** | $16892 | $24555 | $20514 |
| **09/23** | $15819 | $23386 | $19278 |
| **10/23** | $14395 | $22766 | $17940 |
| **11/23** | $15819 | $24888 | $19530 |
| **12/23** | $17475 | $26209 | $21706 |
| **01/24** | $17195 | $26499 | $21215 |
| **02/24** | $18478 | $27933 | $22935 |
| **03/24** | $19155 | $28835 | $23553 |
| **04/24** | $17872 | $27566 | $21798 |
| **05/24** | $18152 | $28868 | $22682 |
| **06/24** | $17988 | $29762 | $22560 |
| **07/24** | $18875 | $30315 | $23935 |
| **08/24** | $19108 | $30975 | $23749 |
| **09/24** | $19622 | $31616 | $24137 |
| **10/24** | $19528 | $31384 | $24077 |
| **11/24** | $21395 | $33471 | $26942 |
| **12/24** | $19948 | $32448 | $24723 |
| **01/25** | $20462 | $33473 | $25669 |
| **02/25** | $18828 | $32831 | $23960 |
| **03/25** | $17195 | $30916 | $22053 |
| **04/25** | $17102 | $30709 | $21982 |
| **05/25** | $18268 | $32655 | $23422 |
| **06/25** | $19202 | $34314 | $24548 |
| **07/25** | $19598 | $35070 | $25123 |
| **08/25** | $20088 | $35881 | $26442 |
| **09/25** | $20602 | $37120 | $27182 |
| **10/25** | $21278 | $37915 | $27877 |
| **11/25** | $21535 | $38019 | $27498 |
| **12/25** | $20858 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class A (excluding sales charges) | 4.56 | 0.83 | 8.27 |
| Class A (including sales charges) | (1.43) | (0.36) | 7.63 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Class A **\|** ASR110_01_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Class A **\|** ASR110_01_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Class C \| LIACX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class C | $185 | 1.82% |

---

## Management's Discussion of Fund Performance
The performance of Class C shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Class C **\|** ASR110_04_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class C shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g44g74.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Class C (including sales charges) ($20537)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9073 | $9436 | $9011 |
| **02/16** | $9005 | $9433 | $9038 |
| **03/16** | $9704 | $10097 | $9734 |
| **04/16** | $9802 | $10159 | $9827 |
| **05/16** | $10084 | $10341 | $10071 |
| **06/16** | $9926 | $10362 | $9997 |
| **07/16** | $10473 | $10774 | $10591 |
| **08/16** | $10527 | $10801 | $10664 |
| **09/16** | $10572 | $10818 | $10695 |
| **10/16** | $10240 | $10584 | $10137 |
| **11/16** | $10904 | $11058 | $10876 |
| **12/16** | $10929 | $11274 | $10973 |
| **01/17** | $11178 | $11486 | $11233 |
| **02/17** | $11571 | $11913 | $11573 |
| **03/17** | $11637 | $11921 | $11659 |
| **04/17** | $11873 | $12047 | $11864 |
| **05/17** | $11991 | $12171 | $11869 |
| **06/17** | $12223 | $12280 | $12140 |
| **07/17** | $12279 | $12512 | $12301 |
| **08/17** | $12321 | $12536 | $12325 |
| **09/17** | $12809 | $12842 | $12841 |
| **10/17** | $13200 | $13122 | $13185 |
| **11/17** | $13563 | $13521 | $13619 |
| **12/17** | $13540 | $13656 | $13656 |
| **01/18** | $14322 | $14375 | $14338 |
| **02/18** | $13828 | $13846 | $13868 |
| **03/18** | $14013 | $13568 | $13981 |
| **04/18** | $13869 | $13619 | $13892 |
| **05/18** | $14754 | $14004 | $14631 |
| **06/18** | $14869 | $14095 | $14754 |
| **07/18** | $15201 | $14563 | $15030 |
| **08/18** | $16156 | $15074 | $16046 |
| **09/18** | $15912 | $15099 | $15811 |
| **10/18** | $13981 | $13988 | $13912 |
| **11/18** | $14358 | $14268 | $14175 |
| **12/18** | $12746 | $12940 | $12637 |
| **01/19** | $14050 | $14051 | $14141 |
| **02/19** | $14893 | $14545 | $15073 |
| **03/19** | $14811 | $14757 | $15036 |
| **04/19** | $15382 | $15346 | $15562 |
| **05/19** | $14512 | $14353 | $14528 |
| **06/19** | $15356 | $15361 | $15659 |
| **07/19** | $15634 | $15590 | $15903 |
| **08/19** | $15078 | $15272 | $15451 |
| **09/19** | $14738 | $15540 | $15161 |
| **10/19** | $14893 | $15874 | $15550 |
| **11/19** | $15820 | $16478 | $16609 |
| **12/19** | $15948 | $16954 | $16763 |
| **01/20** | $15909 | $16935 | $16781 |
| **02/20** | $14677 | $15549 | $15643 |
| **03/20** | $12520 | $13410 | $12871 |
| **04/20** | $14253 | $15187 | $14935 |
| **05/20** | $15871 | $15999 | $16494 |
| **06/20** | $16059 | $16364 | $17101 |
| **07/20** | $16938 | $17294 | $18037 |
| **08/20** | $17401 | $18546 | $18849 |
| **09/20** | $17505 | $17871 | $18704 |
| **10/20** | $17574 | $17485 | $18925 |
| **11/20** | $19402 | $19613 | $21682 |
| **12/20** | $20457 | $20495 | $23547 |
| **01/21** | $20786 | $20404 | $24205 |
| **02/21** | $21623 | $21042 | $24965 |
| **03/21** | $20812 | $21796 | $24133 |
| **04/21** | $21496 | $22919 | $24980 |
| **05/21** | $20647 | $23024 | $24286 |
| **06/21** | $21962 | $23592 | $25589 |
| **07/21** | $22199 | $23991 | $25035 |
| **08/21** | $22871 | $24675 | $25662 |
| **09/21** | $21566 | $23568 | $24685 |
| **10/21** | $23292 | $25161 | $25951 |
| **11/21** | $22370 | $24778 | $24614 |
| **12/21** | $22084 | $25754 | $24735 |
| **01/22** | $18575 | $24239 | $21471 |
| **02/22** | $18526 | $23628 | $21536 |
| **03/22** | $18172 | $24395 | $21691 |
| **04/22** | $15597 | $22206 | $19214 |
| **05/22** | $15018 | $22176 | $18748 |
| **06/22** | $13865 | $20321 | $17450 |
| **07/22** | $15966 | $22227 | $19441 |
| **08/22** | $15495 | $21397 | $19072 |
| **09/22** | $14016 | $19413 | $17429 |
| **10/22** | $14941 | $21005 | $18846 |
| **11/22** | $15344 | $22102 | $19406 |
| **12/22** | $14470 | $20808 | $18251 |
| **01/23** | $15898 | $22241 | $20078 |
| **02/23** | $15848 | $21721 | $19761 |
| **03/23** | $15898 | $22302 | $19446 |
| **04/23** | $15697 | $22539 | $19200 |
| **05/23** | $15562 | $22627 | $19179 |
| **06/23** | $16739 | $24172 | $20693 |
| **07/23** | $17243 | $25039 | $21384 |
| **08/23** | $16924 | $24555 | $20514 |
| **09/23** | $15848 | $23386 | $19278 |
| **10/23** | $14420 | $22766 | $17940 |
| **11/23** | $15814 | $24888 | $19530 |
| **12/23** | $17461 | $26209 | $21706 |
| **01/24** | $17176 | $26499 | $21215 |
| **02/24** | $18436 | $27933 | $22935 |
| **03/24** | $19108 | $28835 | $23553 |
| **04/24** | $17831 | $27566 | $21798 |
| **05/24** | $18083 | $28868 | $22682 |
| **06/24** | $17898 | $29762 | $22560 |
| **07/24** | $18789 | $30315 | $23935 |
| **08/24** | $19008 | $30975 | $23749 |
| **09/24** | $19495 | $31616 | $24137 |
| **10/24** | $19394 | $31384 | $24077 |
| **11/24** | $21243 | $33471 | $26942 |
| **12/24** | $19781 | $32448 | $24723 |
| **01/25** | $20285 | $33473 | $25669 |
| **02/25** | $18655 | $32831 | $23960 |
| **03/25** | $17024 | $30916 | $22053 |
| **04/25** | $16924 | $30709 | $21982 |
| **05/25** | $18050 | $32655 | $23422 |
| **06/25** | $18974 | $34314 | $24548 |
| **07/25** | $19361 | $35070 | $25123 |
| **08/25** | $19814 | $35881 | $26442 |
| **09/25** | $20318 | $37120 | $27182 |
| **10/25** | $20974 | $37915 | $27877 |
| **11/25** | $21226 | $38019 | $27498 |
| **12/25** | $20537 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class C (excluding sales charges) | 3.82 | 0.08 | 7.46 |
| Class C (including sales charges) | 2.82 | 0.08 | 7.46 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Class C **\|** ASR110_04_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Class C **\|** ASR110_04_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Class S \| ACRSX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class S | $84 | 0.82% |

---

## Management's Discussion of Fund Performance
The performance of Class S shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Class S **\|** ASR110_16_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class S shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g04o13.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Class S ($22712)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9080 | $9436 | $9011 |
| **02/16** | $9018 | $9433 | $9038 |
| **03/16** | $9731 | $10097 | $9734 |
| **04/16** | $9835 | $10159 | $9827 |
| **05/16** | $10129 | $10341 | $10071 |
| **06/16** | $9982 | $10362 | $9997 |
| **07/16** | $10536 | $10774 | $10591 |
| **08/16** | $10599 | $10801 | $10664 |
| **09/16** | $10657 | $10818 | $10695 |
| **10/16** | $10328 | $10584 | $10137 |
| **11/16** | $11009 | $11058 | $10876 |
| **12/16** | $11039 | $11274 | $10973 |
| **01/17** | $11298 | $11486 | $11233 |
| **02/17** | $11703 | $11913 | $11573 |
| **03/17** | $11782 | $11921 | $11659 |
| **04/17** | $12035 | $12047 | $11864 |
| **05/17** | $12165 | $12171 | $11869 |
| **06/17** | $12401 | $12280 | $12140 |
| **07/17** | $12469 | $12512 | $12301 |
| **08/17** | $12528 | $12536 | $12325 |
| **09/17** | $13036 | $12842 | $12841 |
| **10/17** | $13447 | $13122 | $13185 |
| **11/17** | $13827 | $13521 | $13619 |
| **12/17** | $13825 | $13656 | $13656 |
| **01/18** | $14615 | $14375 | $14338 |
| **02/18** | $14139 | $13846 | $13868 |
| **03/18** | $14319 | $13568 | $13981 |
| **04/18** | $14202 | $13619 | $13892 |
| **05/18** | $15100 | $14004 | $14631 |
| **06/18** | $15250 | $14095 | $14754 |
| **07/18** | $15605 | $14563 | $15030 |
| **08/18** | $16596 | $15074 | $16046 |
| **09/18** | $16353 | $15099 | $15811 |
| **10/18** | $14371 | $13988 | $13912 |
| **11/18** | $14792 | $14268 | $14175 |
| **12/18** | $13121 | $12940 | $12637 |
| **01/19** | $14486 | $14051 | $14141 |
| **02/19** | $15365 | $14545 | $15073 |
| **03/19** | $15295 | $14757 | $15036 |
| **04/19** | $15891 | $15346 | $15562 |
| **05/19** | $15022 | $14353 | $14528 |
| **06/19** | $15902 | $15361 | $15659 |
| **07/19** | $16208 | $15590 | $15903 |
| **08/19** | $15659 | $15272 | $15451 |
| **09/19** | $15310 | $15540 | $15161 |
| **10/19** | $15479 | $15874 | $15550 |
| **11/19** | $16451 | $16478 | $16609 |
| **12/19** | $16612 | $16954 | $16763 |
| **01/20** | $16578 | $16935 | $16781 |
| **02/20** | $15312 | $15549 | $15643 |
| **03/20** | $13075 | $13410 | $12871 |
| **04/20** | $14871 | $15187 | $14935 |
| **05/20** | $16612 | $15999 | $16494 |
| **06/20** | $16780 | $16364 | $17101 |
| **07/20** | $17729 | $17294 | $18037 |
| **08/20** | $18227 | $18546 | $18849 |
| **09/20** | $18357 | $17871 | $18704 |
| **10/20** | $18440 | $17485 | $18925 |
| **11/20** | $20385 | $19613 | $21682 |
| **12/20** | $21514 | $20495 | $23547 |
| **01/21** | $21877 | $20404 | $24205 |
| **02/21** | $22771 | $21042 | $24965 |
| **03/21** | $21929 | $21796 | $24133 |
| **04/21** | $22681 | $22919 | $24980 |
| **05/21** | $21799 | $23024 | $24286 |
| **06/21** | $23209 | $23592 | $25589 |
| **07/21** | $23466 | $23991 | $25035 |
| **08/21** | $24209 | $24675 | $25662 |
| **09/21** | $22844 | $23568 | $24685 |
| **10/21** | $24696 | $25161 | $25951 |
| **11/21** | $23736 | $24778 | $24614 |
| **12/21** | $23448 | $25754 | $24735 |
| **01/22** | $19754 | $24239 | $21471 |
| **02/22** | $19705 | $23628 | $21536 |
| **03/22** | $19342 | $24395 | $21691 |
| **04/22** | $16621 | $22206 | $19214 |
| **05/22** | $16011 | $22176 | $18748 |
| **06/22** | $14784 | $20321 | $17450 |
| **07/22** | $17052 | $22227 | $19441 |
| **08/22** | $16567 | $21397 | $19072 |
| **09/22** | $14992 | $19413 | $17429 |
| **10/22** | $15996 | $21005 | $18846 |
| **11/22** | $16446 | $22102 | $19406 |
| **12/22** | $15528 | $20808 | $18251 |
| **01/23** | $17069 | $22241 | $20078 |
| **02/23** | $17034 | $21721 | $19761 |
| **03/23** | $17086 | $22302 | $19446 |
| **04/23** | $16896 | $22539 | $19200 |
| **05/23** | $16757 | $22627 | $19179 |
| **06/23** | $18056 | $24172 | $20693 |
| **07/23** | $18610 | $25039 | $21384 |
| **08/23** | $18281 | $24555 | $20514 |
| **09/23** | $17121 | $23386 | $19278 |
| **10/23** | $15597 | $22766 | $17940 |
| **11/23** | $17121 | $24888 | $19530 |
| **12/23** | $18921 | $26209 | $21706 |
| **01/24** | $18627 | $26499 | $21215 |
| **02/24** | $20012 | $27933 | $22935 |
| **03/24** | $20739 | $28835 | $23553 |
| **04/24** | $19371 | $27566 | $21798 |
| **05/24** | $19666 | $28868 | $22682 |
| **06/24** | $19493 | $29762 | $22560 |
| **07/24** | $20479 | $30315 | $23935 |
| **08/24** | $20722 | $30975 | $23749 |
| **09/24** | $21276 | $31616 | $24137 |
| **10/24** | $21189 | $31384 | $24077 |
| **11/24** | $23232 | $33471 | $26942 |
| **12/24** | $21656 | $32448 | $24723 |
| **01/25** | $22210 | $33473 | $25669 |
| **02/25** | $20445 | $32831 | $23960 |
| **03/25** | $18662 | $30916 | $22053 |
| **04/25** | $18575 | $30709 | $21982 |
| **05/25** | $19839 | $32655 | $23422 |
| **06/25** | $20877 | $34314 | $24548 |
| **07/25** | $21310 | $35070 | $25123 |
| **08/25** | $21830 | $35881 | $26442 |
| **09/25** | $22418 | $37120 | $27182 |
| **10/25** | $23145 | $37915 | $27877 |
| **11/25** | $23439 | $38019 | $27498 |
| **12/25** | $22712 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class S<sup>Footnote Reference(a)</sup> | 4.88 | 1.09 | 8.55 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The returns shown for periods prior to October 2, 2024 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Class S **\|** ASR110_16_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Class S **\|** ASR110_16_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Institutional 2 Class \| CRBRX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 2 Class | $80 | 0.78% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 2 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Institutional 2 Class **\|** ASR110_15_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 2 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g53s73.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Institutional 2 Class ($22768)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9081 | $9436 | $9011 |
| **02/16** | $9021 | $9433 | $9038 |
| **03/16** | $9729 | $10097 | $9734 |
| **04/16** | $9839 | $10159 | $9827 |
| **05/16** | $10131 | $10341 | $10071 |
| **06/16** | $9982 | $10362 | $9997 |
| **07/16** | $10534 | $10774 | $10591 |
| **08/16** | $10607 | $10801 | $10664 |
| **09/16** | $10657 | $10818 | $10695 |
| **10/16** | $10333 | $10584 | $10137 |
| **11/16** | $11014 | $11058 | $10876 |
| **12/16** | $11043 | $11274 | $10973 |
| **01/17** | $11300 | $11486 | $11233 |
| **02/17** | $11708 | $11913 | $11573 |
| **03/17** | $11785 | $11921 | $11659 |
| **04/17** | $12041 | $12047 | $11864 |
| **05/17** | $12166 | $12171 | $11869 |
| **06/17** | $12407 | $12280 | $12140 |
| **07/17** | $12471 | $12512 | $12301 |
| **08/17** | $12528 | $12536 | $12325 |
| **09/17** | $13043 | $12842 | $12841 |
| **10/17** | $13451 | $13122 | $13185 |
| **11/17** | $13830 | $13521 | $13619 |
| **12/17** | $13827 | $13656 | $13656 |
| **01/18** | $14621 | $14375 | $14338 |
| **02/18** | $14143 | $13846 | $13868 |
| **03/18** | $14331 | $13568 | $13981 |
| **04/18** | $14203 | $13619 | $13892 |
| **05/18** | $15116 | $14004 | $14631 |
| **06/18** | $15261 | $14095 | $14754 |
| **07/18** | $15615 | $14563 | $15030 |
| **08/18** | $16600 | $15074 | $16046 |
| **09/18** | $16360 | $15099 | $15811 |
| **10/18** | $14383 | $13988 | $13912 |
| **11/18** | $14799 | $14268 | $14175 |
| **12/18** | $13136 | $12940 | $12637 |
| **01/19** | $14501 | $14051 | $14141 |
| **02/19** | $15379 | $14545 | $15073 |
| **03/19** | $15312 | $14757 | $15036 |
| **04/19** | $15904 | $15346 | $15562 |
| **05/19** | $15026 | $14353 | $14528 |
| **06/19** | $15914 | $15361 | $15659 |
| **07/19** | $16223 | $15590 | $15903 |
| **08/19** | $15665 | $15272 | $15451 |
| **09/19** | $15327 | $15540 | $15161 |
| **10/19** | $15486 | $15874 | $15550 |
| **11/19** | $16472 | $16478 | $16609 |
| **12/19** | $16634 | $16954 | $16763 |
| **01/20** | $16591 | $16935 | $16781 |
| **02/20** | $15319 | $15549 | $15643 |
| **03/20** | $13082 | $13410 | $12871 |
| **04/20** | $14895 | $15187 | $14935 |
| **05/20** | $16623 | $15999 | $16494 |
| **06/20** | $16802 | $16364 | $17101 |
| **07/20** | $17745 | $17294 | $18037 |
| **08/20** | $18244 | $18546 | $18849 |
| **09/20** | $18388 | $17871 | $18704 |
| **10/20** | $18466 | $17485 | $18925 |
| **11/20** | $20407 | $19613 | $21682 |
| **12/20** | $21541 | $20495 | $23547 |
| **01/21** | $21915 | $20404 | $24205 |
| **02/21** | $22806 | $21042 | $24965 |
| **03/21** | $21963 | $21796 | $24133 |
| **04/21** | $22710 | $22919 | $24980 |
| **05/21** | $21830 | $23024 | $24286 |
| **06/21** | $23244 | $23592 | $25589 |
| **07/21** | $23507 | $23991 | $25035 |
| **08/21** | $24246 | $24675 | $25662 |
| **09/21** | $22868 | $23568 | $24685 |
| **10/21** | $24735 | $25161 | $25951 |
| **11/21** | $23783 | $24778 | $24614 |
| **12/21** | $23500 | $25754 | $24735 |
| **01/22** | $19784 | $24239 | $21471 |
| **02/22** | $19739 | $23628 | $21536 |
| **03/22** | $19377 | $24395 | $21691 |
| **04/22** | $16654 | $22206 | $19214 |
| **05/22** | $16038 | $22176 | $18748 |
| **06/22** | $14812 | $20321 | $17450 |
| **07/22** | $17076 | $22227 | $19441 |
| **08/22** | $16589 | $21397 | $19072 |
| **09/22** | $15016 | $19413 | $17429 |
| **10/22** | $16023 | $21005 | $18846 |
| **11/22** | $16479 | $22102 | $19406 |
| **12/22** | $15551 | $20808 | $18251 |
| **01/23** | $17092 | $22241 | $20078 |
| **02/23** | $17060 | $21721 | $19761 |
| **03/23** | $17123 | $22302 | $19446 |
| **04/23** | $16935 | $22539 | $19200 |
| **05/23** | $16793 | $22627 | $19179 |
| **06/23** | $18098 | $24172 | $20693 |
| **07/23** | $18648 | $25039 | $21384 |
| **08/23** | $18318 | $24555 | $20514 |
| **09/23** | $17155 | $23386 | $19278 |
| **10/23** | $15629 | $22766 | $17940 |
| **11/23** | $17155 | $24888 | $19530 |
| **12/23** | $18963 | $26209 | $21706 |
| **01/24** | $18680 | $26499 | $21215 |
| **02/24** | $20064 | $27933 | $22935 |
| **03/24** | $20803 | $28835 | $23553 |
| **04/24** | $19419 | $27566 | $21798 |
| **05/24** | $19718 | $28868 | $22682 |
| **06/24** | $19545 | $29762 | $22560 |
| **07/24** | $20520 | $30315 | $23935 |
| **08/24** | $20787 | $30975 | $23749 |
| **09/24** | $21337 | $31616 | $24137 |
| **10/24** | $21243 | $31384 | $24077 |
| **11/24** | $23287 | $33471 | $26942 |
| **12/24** | $21715 | $32448 | $24723 |
| **01/25** | $22281 | $33473 | $25669 |
| **02/25** | $20504 | $32831 | $23960 |
| **03/25** | $18711 | $30916 | $22053 |
| **04/25** | $18633 | $30709 | $21982 |
| **05/25** | $19891 | $32655 | $23422 |
| **06/25** | $20928 | $34314 | $24548 |
| **07/25** | $21369 | $35070 | $25123 |
| **08/25** | $21903 | $35881 | $26442 |
| **09/25** | $22469 | $37120 | $27182 |
| **10/25** | $23208 | $37915 | $27877 |
| **11/25** | $23507 | $38019 | $27498 |
| **12/25** | $22768 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 2 Class | 4.85 | 1.11 | 8.58 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Institutional 2 Class **\|** ASR110_15_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Institutional 2 Class **\|** ASR110_15_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Institutional 3 Class \| CRBYX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 3 Class | $76 | 0.74% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 3 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Institutional 3 Class **\|** ASR110_17_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 3 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g22w21.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Institutional 3 Class ($22876)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9085 | $9436 | $9011 |
| **02/16** | $9020 | $9433 | $9038 |
| **03/16** | $9730 | $10097 | $9734 |
| **04/16** | $9840 | $10159 | $9827 |
| **05/16** | $10135 | $10341 | $10071 |
| **06/16** | $9982 | $10362 | $9997 |
| **07/16** | $10538 | $10774 | $10591 |
| **08/16** | $10610 | $10801 | $10664 |
| **09/16** | $10665 | $10818 | $10695 |
| **10/16** | $10338 | $10584 | $10137 |
| **11/16** | $11015 | $11058 | $10876 |
| **12/16** | $11050 | $11274 | $10973 |
| **01/17** | $11305 | $11486 | $11233 |
| **02/17** | $11712 | $11913 | $11573 |
| **03/17** | $11794 | $11921 | $11659 |
| **04/17** | $12049 | $12047 | $11864 |
| **05/17** | $12173 | $12171 | $11869 |
| **06/17** | $12413 | $12280 | $12140 |
| **07/17** | $12484 | $12512 | $12301 |
| **08/17** | $12548 | $12536 | $12325 |
| **09/17** | $13060 | $12842 | $12841 |
| **10/17** | $13473 | $13122 | $13185 |
| **11/17** | $13850 | $13521 | $13619 |
| **12/17** | $13847 | $13656 | $13656 |
| **01/18** | $14644 | $14375 | $14338 |
| **02/18** | $14169 | $13846 | $13868 |
| **03/18** | $14356 | $13568 | $13981 |
| **04/18** | $14229 | $13619 | $13892 |
| **05/18** | $15135 | $14004 | $14631 |
| **06/18** | $15285 | $14095 | $14754 |
| **07/18** | $15637 | $14563 | $15030 |
| **08/18** | $16632 | $15074 | $16046 |
| **09/18** | $16395 | $15099 | $15811 |
| **10/18** | $14414 | $13988 | $13912 |
| **11/18** | $14827 | $14268 | $14175 |
| **12/18** | $13157 | $12940 | $12637 |
| **01/19** | $14531 | $14051 | $14141 |
| **02/19** | $15412 | $14545 | $15073 |
| **03/19** | $15346 | $14757 | $15036 |
| **04/19** | $15942 | $15346 | $15562 |
| **05/19** | $15061 | $14353 | $14528 |
| **06/19** | $15952 | $15361 | $15659 |
| **07/19** | $16258 | $15590 | $15903 |
| **08/19** | $15706 | $15272 | $15451 |
| **09/19** | $15360 | $15540 | $15161 |
| **10/19** | $15528 | $15874 | $15550 |
| **11/19** | $16505 | $16478 | $16609 |
| **12/19** | $16676 | $16954 | $16763 |
| **01/20** | $16633 | $16935 | $16781 |
| **02/20** | $15362 | $15549 | $15643 |
| **03/20** | $13124 | $13410 | $12871 |
| **04/20** | $14931 | $15187 | $14935 |
| **05/20** | $16676 | $15999 | $16494 |
| **06/20** | $16853 | $16364 | $17101 |
| **07/20** | $17798 | $17294 | $18037 |
| **08/20** | $18303 | $18546 | $18849 |
| **09/20** | $18435 | $17871 | $18704 |
| **10/20** | $18523 | $17485 | $18925 |
| **11/20** | $20468 | $19613 | $21682 |
| **12/20** | $21602 | $20495 | $23547 |
| **01/21** | $21983 | $20404 | $24205 |
| **02/21** | $22878 | $21042 | $24965 |
| **03/21** | $22031 | $21796 | $24133 |
| **04/21** | $22782 | $22919 | $24980 |
| **05/21** | $21900 | $23024 | $24286 |
| **06/21** | $23318 | $23592 | $25589 |
| **07/21** | $23590 | $23991 | $25035 |
| **08/21** | $24334 | $24675 | $25662 |
| **09/21** | $22958 | $23568 | $24685 |
| **10/21** | $24818 | $25161 | $25951 |
| **11/21** | $23863 | $24778 | $24614 |
| **12/21** | $23581 | $25754 | $24735 |
| **01/22** | $19854 | $24239 | $21471 |
| **02/22** | $19810 | $23628 | $21536 |
| **03/22** | $19438 | $24395 | $21691 |
| **04/22** | $16721 | $22206 | $19214 |
| **05/22** | $16097 | $22176 | $18748 |
| **06/22** | $14873 | $20321 | $17450 |
| **07/22** | $17137 | $22227 | $19441 |
| **08/22** | $16657 | $21397 | $19072 |
| **09/22** | $15075 | $19413 | $17429 |
| **10/22** | $16083 | $21005 | $18846 |
| **11/22** | $16533 | $22102 | $19406 |
| **12/22** | $15617 | $20808 | $18251 |
| **01/23** | $17168 | $22241 | $20078 |
| **02/23** | $17122 | $21721 | $19761 |
| **03/23** | $17199 | $22302 | $19446 |
| **04/23** | $16998 | $22539 | $19200 |
| **05/23** | $16858 | $22627 | $19179 |
| **06/23** | $18161 | $24172 | $20693 |
| **07/23** | $18704 | $25039 | $21384 |
| **08/23** | $18394 | $24555 | $20514 |
| **09/23** | $17215 | $23386 | $19278 |
| **10/23** | $15680 | $22766 | $17940 |
| **11/23** | $17230 | $24888 | $19530 |
| **12/23** | $19045 | $26209 | $21706 |
| **01/24** | $18750 | $26499 | $21215 |
| **02/24** | $20131 | $27933 | $22935 |
| **03/24** | $20875 | $28835 | $23553 |
| **04/24** | $19495 | $27566 | $21798 |
| **05/24** | $19789 | $28868 | $22682 |
| **06/24** | $19619 | $29762 | $22560 |
| **07/24** | $20611 | $30315 | $23935 |
| **08/24** | $20859 | $30975 | $23749 |
| **09/24** | $21418 | $31616 | $24137 |
| **10/24** | $21340 | $31384 | $24077 |
| **11/24** | $23387 | $33471 | $26942 |
| **12/24** | $21806 | $32448 | $24723 |
| **01/25** | $22364 | $33473 | $25669 |
| **02/25** | $20596 | $32831 | $23960 |
| **03/25** | $18797 | $30916 | $22053 |
| **04/25** | $18719 | $30709 | $21982 |
| **05/25** | $19975 | $32655 | $23422 |
| **06/25** | $21015 | $34314 | $24548 |
| **07/25** | $21464 | $35070 | $25123 |
| **08/25** | $21992 | $35881 | $26442 |
| **09/25** | $22581 | $37120 | $27182 |
| **10/25** | $23325 | $37915 | $27877 |
| **11/25** | $23620 | $38019 | $27498 |
| **12/25** | $22876 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 3 Class | 4.91 | 1.15 | 8.63 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Institutional 3 Class **\|** ASR110_17_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Institutional 3 Class **\|** ASR110_17_(02/26) \|

# Columbia Acorn<sup>®</sup> Fund
Institutional Class \| ACRNX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn<sup>®</sup> Fund (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional Class | $84 | 0.82% |

---

## Management's Discussion of Fund Performance
The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the consumer discretionary, energy and industrials sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the industrials and health care sectors and smaller allocations to the financials and communication services sectors buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Celestica Inc., an electronic component manufacturer; Exact Sciences Corporation, a cancer screening and diagnostics company; Aerovironment Inc., a robotics systems developer; Curtiss-Wright Corporation, which builds high-precision parts for airplanes, the military, and nuclear power systems; and Coherent Corp., which makes lasers, optical parts, and high tech materials, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the health care, information technology, financials and consumer staples sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| A large weighting in the consumer staples sector and a small allocation to the utilities sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Globant SA, which helps organizations build modern digital technology like apps, websites, AI systems, and software; Parsons Corporation, a developer of national security and cybersecurity systems to protect roads, bridges, airports, and water systems; Glaukos Corp., a medical technology and pharmaceutical company; Credo Technology Group, a developer of connectivity solutions; and Blue Owl Capital, an asset management firm, were top detractors from the Fund's relative performance during the period.

Columbia Acorn<sup>®</sup> Fund \| Institutional Class **\|** ASR110_08_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g25v93.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn<sup>®</sup> Fund Institutional Class ($22695)** | **Russell 3000<sup>®</sup> Index ($38012)** | **Russell 2500<sup>®</sup> Growth Index ($27272)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9080 | $9436 | $9011 |
| **02/16** | $9018 | $9433 | $9038 |
| **03/16** | $9731 | $10097 | $9734 |
| **04/16** | $9835 | $10159 | $9827 |
| **05/16** | $10129 | $10341 | $10071 |
| **06/16** | $9982 | $10362 | $9997 |
| **07/16** | $10536 | $10774 | $10591 |
| **08/16** | $10599 | $10801 | $10664 |
| **09/16** | $10657 | $10818 | $10695 |
| **10/16** | $10328 | $10584 | $10137 |
| **11/16** | $11009 | $11058 | $10876 |
| **12/16** | $11039 | $11274 | $10973 |
| **01/17** | $11298 | $11486 | $11233 |
| **02/17** | $11703 | $11913 | $11573 |
| **03/17** | $11782 | $11921 | $11659 |
| **04/17** | $12035 | $12047 | $11864 |
| **05/17** | $12165 | $12171 | $11869 |
| **06/17** | $12401 | $12280 | $12140 |
| **07/17** | $12469 | $12512 | $12301 |
| **08/17** | $12528 | $12536 | $12325 |
| **09/17** | $13036 | $12842 | $12841 |
| **10/17** | $13447 | $13122 | $13185 |
| **11/17** | $13827 | $13521 | $13619 |
| **12/17** | $13825 | $13656 | $13656 |
| **01/18** | $14615 | $14375 | $14338 |
| **02/18** | $14139 | $13846 | $13868 |
| **03/18** | $14319 | $13568 | $13981 |
| **04/18** | $14202 | $13619 | $13892 |
| **05/18** | $15100 | $14004 | $14631 |
| **06/18** | $15250 | $14095 | $14754 |
| **07/18** | $15605 | $14563 | $15030 |
| **08/18** | $16596 | $15074 | $16046 |
| **09/18** | $16353 | $15099 | $15811 |
| **10/18** | $14371 | $13988 | $13912 |
| **11/18** | $14792 | $14268 | $14175 |
| **12/18** | $13121 | $12940 | $12637 |
| **01/19** | $14486 | $14051 | $14141 |
| **02/19** | $15365 | $14545 | $15073 |
| **03/19** | $15295 | $14757 | $15036 |
| **04/19** | $15891 | $15346 | $15562 |
| **05/19** | $15022 | $14353 | $14528 |
| **06/19** | $15902 | $15361 | $15659 |
| **07/19** | $16208 | $15590 | $15903 |
| **08/19** | $15659 | $15272 | $15451 |
| **09/19** | $15310 | $15540 | $15161 |
| **10/19** | $15479 | $15874 | $15550 |
| **11/19** | $16451 | $16478 | $16609 |
| **12/19** | $16612 | $16954 | $16763 |
| **01/20** | $16578 | $16935 | $16781 |
| **02/20** | $15312 | $15549 | $15643 |
| **03/20** | $13075 | $13410 | $12871 |
| **04/20** | $14871 | $15187 | $14935 |
| **05/20** | $16612 | $15999 | $16494 |
| **06/20** | $16780 | $16364 | $17101 |
| **07/20** | $17729 | $17294 | $18037 |
| **08/20** | $18227 | $18546 | $18849 |
| **09/20** | $18357 | $17871 | $18704 |
| **10/20** | $18440 | $17485 | $18925 |
| **11/20** | $20385 | $19613 | $21682 |
| **12/20** | $21514 | $20495 | $23547 |
| **01/21** | $21877 | $20404 | $24205 |
| **02/21** | $22771 | $21042 | $24965 |
| **03/21** | $21929 | $21796 | $24133 |
| **04/21** | $22681 | $22919 | $24980 |
| **05/21** | $21799 | $23024 | $24286 |
| **06/21** | $23209 | $23592 | $25589 |
| **07/21** | $23466 | $23991 | $25035 |
| **08/21** | $24209 | $24675 | $25662 |
| **09/21** | $22844 | $23568 | $24685 |
| **10/21** | $24696 | $25161 | $25951 |
| **11/21** | $23736 | $24778 | $24614 |
| **12/21** | $23448 | $25754 | $24735 |
| **01/22** | $19754 | $24239 | $21471 |
| **02/22** | $19705 | $23628 | $21536 |
| **03/22** | $19342 | $24395 | $21691 |
| **04/22** | $16621 | $22206 | $19214 |
| **05/22** | $16011 | $22176 | $18748 |
| **06/22** | $14784 | $20321 | $17450 |
| **07/22** | $17052 | $22227 | $19441 |
| **08/22** | $16567 | $21397 | $19072 |
| **09/22** | $14992 | $19413 | $17429 |
| **10/22** | $15996 | $21005 | $18846 |
| **11/22** | $16446 | $22102 | $19406 |
| **12/22** | $15528 | $20808 | $18251 |
| **01/23** | $17069 | $22241 | $20078 |
| **02/23** | $17034 | $21721 | $19761 |
| **03/23** | $17086 | $22302 | $19446 |
| **04/23** | $16896 | $22539 | $19200 |
| **05/23** | $16757 | $22627 | $19179 |
| **06/23** | $18056 | $24172 | $20693 |
| **07/23** | $18610 | $25039 | $21384 |
| **08/23** | $18281 | $24555 | $20514 |
| **09/23** | $17121 | $23386 | $19278 |
| **10/23** | $15597 | $22766 | $17940 |
| **11/23** | $17121 | $24888 | $19530 |
| **12/23** | $18921 | $26209 | $21706 |
| **01/24** | $18627 | $26499 | $21215 |
| **02/24** | $20012 | $27933 | $22935 |
| **03/24** | $20739 | $28835 | $23553 |
| **04/24** | $19371 | $27566 | $21798 |
| **05/24** | $19666 | $28868 | $22682 |
| **06/24** | $19493 | $29762 | $22560 |
| **07/24** | $20479 | $30315 | $23935 |
| **08/24** | $20722 | $30975 | $23749 |
| **09/24** | $21276 | $31616 | $24137 |
| **10/24** | $21189 | $31384 | $24077 |
| **11/24** | $23232 | $33471 | $26942 |
| **12/24** | $21656 | $32448 | $24723 |
| **01/25** | $22210 | $33473 | $25669 |
| **02/25** | $20445 | $32831 | $23960 |
| **03/25** | $18662 | $30916 | $22053 |
| **04/25** | $18575 | $30709 | $21982 |
| **05/25** | $19839 | $32655 | $23422 |
| **06/25** | $20860 | $34314 | $24548 |
| **07/25** | $21310 | $35070 | $25123 |
| **08/25** | $21830 | $35881 | $26442 |
| **09/25** | $22418 | $37120 | $27182 |
| **10/25** | $23145 | $37915 | $27877 |
| **11/25** | $23439 | $38019 | $27498 |
| **12/25** | $22695 | $38012 | $27272 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional Class | 4.80 | 1.07 | 8.54 |
| Russell 3000<sup>®</sup> Index | 17.15 | 13.15 | 14.29 |
| Russell 2500<sup>®</sup> Growth Index | 10.31 | 2.98 | 10.55 |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $2435860719 |
| **Total number of portfolio holdings** | 114 |
| **Management services fees (represents 0.71% of Fund average net assets)** | $17699069 |
| **Portfolio turnover for the reporting period** | 78% |

---

Columbia Acorn<sup>®</sup> Fund \| Institutional Class **\|** ASR110_08_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.2% |
| Health Care | 20.9% |
| Information Technology | 19.8% |
| Consumer Discretionary | 11.0% |
| Financials | 10.6% |
| Consumer Staples | 4.6% |
| Energy | 1.9% |
| Real Estate | 1.5% |
| Communication Services | 0.8% |

---

### Top Holdings

---

| | |
|:---|:---|
| Celestica, Inc. | 2.2% |
| Churchill Downs, Inc. | 2.1% |
| Insmed, Inc. | 2.1% |
| GCM Grosvenor, Inc., Class A | 2.1% |
| Carlyle Group, Inc. (The) | 2.0% |
| Wingstop, Inc. | 2.0% |
| TopBuild Corp. | 2.0% |
| VSE Corp. | 2.0% |
| FTAI Aviation Ltd. | 1.8% |
| Cavco Industries, Inc. | 1.8% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Common Stocks | 98.3% |
| Exchange-Traded Equity Funds | 1.0% |
| Other | 0.6% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn<sup>®</sup> Fund \| Institutional Class **\|** ASR110_08_(02/26) \|

# Columbia Acorn International<sup>®</sup>
Class A \| LAIAX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International<sup>®</sup> (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class A | $128 | 1.21% |

---

## Management's Discussion of Fund Performance
The performance of Class A shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and information technology sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A smaller allocation to the consumer discretionary sector buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Bank of Ireland, an Irish diversified financial services company; BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer; and Simplex Holdings, a Japanese system development and financial solutions provider, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, communication services, consumer staples, health care and materials sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the communication services and real estate sectors and small allocations to the industrials and materials sectors detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Silergy Corp., a Taiwanese manufacturer of power management integrated circuits; Interparfums, a perfume and fragrance manufacturer; IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Amplifon SpA, an Italian maker of customized hearing solutions; and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International<sup>®</sup> \| Class A **\|** ASR111_01_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g31i20.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International<sup>®</sup> Class A (including sales charges) ($14297)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE SMID Cap Growth Index (Net) ($18583)** |
| **12/15** | $9426 | $10000 | $10000 |
| **01/16** | $8929 | $9277 | $9249 |
| **02/16** | $8830 | $9107 | $9207 |
| **03/16** | $9431 | $9699 | $9908 |
| **04/16** | $9477 | $9980 | $10071 |
| **05/16** | $9506 | $9890 | $10123 |
| **06/16** | $9292 | $9558 | $9712 |
| **07/16** | $9737 | $10042 | $10271 |
| **08/16** | $9805 | $10049 | $10129 |
| **09/16** | $10052 | $10173 | $10363 |
| **10/16** | $9569 | $9965 | $9941 |
| **11/16** | $9132 | $9766 | $9627 |
| **12/16** | $9190 | $10100 | $9827 |
| **01/17** | $9572 | $10393 | $10233 |
| **02/17** | $9777 | $10542 | $10418 |
| **03/17** | $10077 | $10832 | $10673 |
| **04/17** | $10528 | $11107 | $11103 |
| **05/17** | $10927 | $11515 | $11609 |
| **06/17** | $10883 | $11495 | $11556 |
| **07/17** | $11171 | $11826 | $11921 |
| **08/17** | $11156 | $11822 | $12030 |
| **09/17** | $11407 | $12116 | $12360 |
| **10/17** | $11633 | $12300 | $12653 |
| **11/17** | $11869 | $12429 | $12813 |
| **12/17** | $12122 | $12628 | $13084 |
| **01/18** | $12763 | $13262 | $13775 |
| **02/18** | $12265 | $12663 | $13256 |
| **03/18** | $12380 | $12435 | $13070 |
| **04/18** | $12378 | $12719 | $13192 |
| **05/18** | $12351 | $12433 | $13228 |
| **06/18** | $12115 | $12281 | $13032 |
| **07/18** | $12271 | $12584 | $13180 |
| **08/18** | $12171 | $12341 | $13139 |
| **09/18** | $12069 | $12448 | $13010 |
| **10/18** | $10764 | $11457 | $11634 |
| **11/18** | $10785 | $11442 | $11482 |
| **12/18** | $10167 | $10887 | $10806 |
| **01/19** | $11026 | $11602 | $11619 |
| **02/19** | $11360 | $11898 | $11943 |
| **03/19** | $11433 | $11973 | $12041 |
| **04/19** | $11888 | $12310 | $12469 |
| **05/19** | $11377 | $11719 | $11849 |
| **06/19** | $12035 | $12414 | $12482 |
| **07/19** | $11804 | $12256 | $12440 |
| **08/19** | $11609 | $11939 | $12181 |
| **09/19** | $11653 | $12281 | $12384 |
| **10/19** | $12252 | $12722 | $12896 |
| **11/19** | $12652 | $12866 | $13260 |
| **12/19** | $13173 | $13284 | $13726 |
| **01/20** | $12733 | $13006 | $13497 |
| **02/20** | $11690 | $11831 | $12252 |
| **03/20** | $9413 | $10252 | $10568 |
| **04/20** | $10542 | $10914 | $11675 |
| **05/20** | $11613 | $11389 | $12666 |
| **06/20** | $11971 | $11777 | $12935 |
| **07/20** | $12612 | $12051 | $13555 |
| **08/20** | $13232 | $12671 | $14425 |
| **09/20** | $13265 | $12342 | $14406 |
| **10/20** | $12863 | $11849 | $13944 |
| **11/20** | $14043 | $13686 | $15562 |
| **12/20** | $15106 | $14322 | $16468 |
| **01/21** | $15150 | $14169 | $16344 |
| **02/21** | $15084 | $14487 | $16247 |
| **03/21** | $15084 | $14820 | $16455 |
| **04/21** | $16057 | $15266 | $17236 |
| **05/21** | $16321 | $15764 | $17564 |
| **06/21** | $16352 | $15587 | $17542 |
| **07/21** | $16810 | $15704 | $17884 |
| **08/21** | $17200 | $15981 | $18334 |
| **09/21** | $16415 | $15517 | $17592 |
| **10/21** | $17005 | $15899 | $17957 |
| **11/21** | $16311 | $15159 | $17165 |
| **12/21** | $17015 | $15935 | $17722 |
| **01/22** | $14698 | $15165 | $15608 |
| **02/22** | $14026 | $14897 | $15320 |
| **03/22** | $13800 | $14993 | $15367 |
| **04/22** | $12416 | $14023 | $14053 |
| **05/22** | $12206 | $14128 | $13845 |
| **06/22** | $10871 | $12817 | $12397 |
| **07/22** | $11922 | $13456 | $13366 |
| **08/22** | $11088 | $12817 | $12634 |
| **09/22** | $9647 | $11618 | $11208 |
| **10/22** | $10164 | $12242 | $11694 |
| **11/22** | $11584 | $13621 | $12903 |
| **12/22** | $11262 | $13632 | $12815 |
| **01/23** | $12428 | $14736 | $13846 |
| **02/23** | $12138 | $14429 | $13475 |
| **03/23** | $12513 | $14786 | $13801 |
| **04/23** | $12645 | $15204 | $14045 |
| **05/23** | $12370 | $14560 | $13607 |
| **06/23** | $12766 | $15223 | $13890 |
| **07/23** | $13077 | $15715 | $14414 |
| **08/23** | $12534 | $15113 | $13847 |
| **09/23** | $11679 | $14597 | $13038 |
| **10/23** | $11051 | $14005 | $12208 |
| **11/23** | $12428 | $15305 | $13638 |
| **12/23** | $13436 | $16118 | $14642 |
| **01/24** | $12835 | $16211 | $14421 |
| **02/24** | $13183 | $16508 | $14758 |
| **03/24** | $13531 | $17051 | $15097 |
| **04/24** | $12850 | $16614 | $14427 |
| **05/24** | $13647 | $17258 | $14983 |
| **06/24** | $13589 | $16979 | $14684 |
| **07/24** | $13867 | $17477 | $15280 |
| **08/24** | $14354 | $18046 | $15785 |
| **09/24** | $14638 | $18212 | $16187 |
| **10/24** | $13359 | $17222 | $15121 |
| **11/24** | $13337 | $17124 | $15261 |
| **12/24** | $12752 | $16735 | $14870 |
| **01/25** | $13463 | $17614 | $15482 |
| **02/25** | $13190 | $17956 | $15390 |
| **03/25** | $12563 | $17883 | $15233 |
| **04/25** | $13486 | $18702 | $16204 |
| **05/25** | $14250 | $19558 | $17188 |
| **06/25** | $14929 | $19989 | $17858 |
| **07/25** | $14371 | $19708 | $17648 |
| **08/25** | $14535 | $20549 | $18263 |
| **09/25** | $14656 | $20942 | $18538 |
| **10/25** | $14474 | $21188 | $18478 |
| **11/25** | $14207 | $21320 | $18303 |
| **12/25** | $14297 | $21959 | $18583 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class A (excluding sales charges)<sup>Footnote Reference(a)</sup> | 12.12 | (1.09) | 4.25 |
| Class A (including sales charges)<sup>Footnote Reference(a)</sup> | 5.69 | (2.26) | 3.64 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE SMID Cap Growth Index (Net) | 24.96 | 2.45 | 6.39 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $805895861 |
| **Total number of portfolio holdings** | 71 |
| **Management services fees (represents 0.86% of Fund average net assets)** | $7533596 |
| **Portfolio turnover for the reporting period** | 25% |

---

Columbia Acorn International<sup>®</sup> \| Class A **\|** ASR111_01_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 39.2% |
| United Kingdom | 16.1% |
| Germany | 6.4% |
| Switzerland | 5.1% |
| Sweden | 4.7% |
| United States | 3.8% |
| Finland | 3.7% |
| Italy | 3.3% |
| France | 2.9% |
| Australia | 2.7% |
| Other | 12.3% |

---

### Top Holdings

---

| | |
|:---|:---|
| Taisei Corp. | 3.0% |
| Halma PLC | 2.7% |
| Niterra Co., Ltd. | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Kokusai Electric Corp. | 2.4% |
| Capcom Co., Ltd. | 2.4% |
| Prysmian SpA | 2.4% |
| Hexagon AB, Class B | 2.2% |
| Fisher & Paykel Healthcare Corp., Ltd. | 2.2% |
| Babcock International Group PLC | 2.2% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 31.0% |
| Information Technology | 22.3% |
| Communication Services | 9.3% |
| Financials | 9.2% |
| Health Care | 5.9% |
| Consumer Discretionary | 5.3% |
| Materials | 5.0% |
| Consumer Staples | 4.9% |
| Real Estate | 4.0% |
| Energy | 2.9% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International<sup>®</sup> \| Class A **\|** ASR111_01_(02/26) \|

# Columbia Acorn International<sup>®</sup>
Class S \| CCIDX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International<sup>®</sup> (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class S | $102 | 0.96% |

---

## Management's Discussion of Fund Performance
The performance of Class S shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and information technology sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A smaller allocation to the consumer discretionary sector buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Bank of Ireland, an Irish diversified financial services company; BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer; and Simplex Holdings, a Japanese system development and financial solutions provider, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, communication services, consumer staples, health care and materials sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the communication services and real estate sectors and small allocations to the industrials and materials sectors detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Silergy Corp., a Taiwanese manufacturer of power management integrated circuits; Interparfums, a perfume and fragrance manufacturer; IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Amplifon SpA, an Italian maker of customized hearing solutions; and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International<sup>®</sup> \| Class S **\|** ASR111_16_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class S shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g96t02.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International<sup>®</sup> Class S ($15549)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE SMID Cap Growth Index (Net) ($18583)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9476 | $9277 | $9249 |
| **02/16** | $9371 | $9107 | $9207 |
| **03/16** | $10013 | $9699 | $9908 |
| **04/16** | $10061 | $9980 | $10071 |
| **05/16** | $10095 | $9890 | $10123 |
| **06/16** | $9871 | $9558 | $9712 |
| **07/16** | $10347 | $10042 | $10271 |
| **08/16** | $10419 | $10049 | $10129 |
| **09/16** | $10684 | $10173 | $10363 |
| **10/16** | $10172 | $9965 | $9941 |
| **11/16** | $9712 | $9766 | $9627 |
| **12/16** | $9772 | $10100 | $9827 |
| **01/17** | $10181 | $10393 | $10233 |
| **02/17** | $10401 | $10542 | $10418 |
| **03/17** | $10723 | $10832 | $10673 |
| **04/17** | $11204 | $11107 | $11103 |
| **05/17** | $11631 | $11515 | $11609 |
| **06/17** | $11587 | $11495 | $11556 |
| **07/17** | $11895 | $11826 | $11921 |
| **08/17** | $11882 | $11822 | $12030 |
| **09/17** | $12151 | $12116 | $12360 |
| **10/17** | $12394 | $12300 | $12653 |
| **11/17** | $12650 | $12429 | $12813 |
| **12/17** | $12922 | $12628 | $13084 |
| **01/18** | $13608 | $13262 | $13775 |
| **02/18** | $13081 | $12663 | $13256 |
| **03/18** | $13205 | $12435 | $13070 |
| **04/18** | $13203 | $12719 | $13192 |
| **05/18** | $13180 | $12433 | $13228 |
| **06/18** | $12931 | $12281 | $13032 |
| **07/18** | $13101 | $12584 | $13180 |
| **08/18** | $12997 | $12341 | $13139 |
| **09/18** | $12888 | $12448 | $13010 |
| **10/18** | $11499 | $11457 | $11634 |
| **11/18** | $11522 | $11442 | $11482 |
| **12/18** | $10865 | $10887 | $10806 |
| **01/19** | $11785 | $11602 | $11619 |
| **02/19** | $12142 | $11898 | $11943 |
| **03/19** | $12223 | $11973 | $12041 |
| **04/19** | $12713 | $12310 | $12469 |
| **05/19** | $12168 | $11719 | $11849 |
| **06/19** | $12877 | $12414 | $12482 |
| **07/19** | $12630 | $12256 | $12440 |
| **08/19** | $12427 | $11939 | $12181 |
| **09/19** | $12474 | $12281 | $12384 |
| **10/19** | $13120 | $12722 | $12896 |
| **11/19** | $13551 | $12866 | $13260 |
| **12/19** | $14112 | $13284 | $13726 |
| **01/20** | $13647 | $13006 | $13497 |
| **02/20** | $12530 | $11831 | $12252 |
| **03/20** | $10091 | $10252 | $10568 |
| **04/20** | $11302 | $10914 | $11675 |
| **05/20** | $12452 | $11389 | $12666 |
| **06/20** | $12844 | $11777 | $12935 |
| **07/20** | $13533 | $12051 | $13555 |
| **08/20** | $14201 | $12671 | $14425 |
| **09/20** | $14240 | $12342 | $14406 |
| **10/20** | $13811 | $11849 | $13944 |
| **11/20** | $15081 | $13686 | $15562 |
| **12/20** | $16227 | $14322 | $16468 |
| **01/21** | $16275 | $14169 | $16344 |
| **02/21** | $16209 | $14487 | $16247 |
| **03/21** | $16209 | $14820 | $16455 |
| **04/21** | $17263 | $15266 | $17236 |
| **05/21** | $17546 | $15764 | $17564 |
| **06/21** | $17586 | $15587 | $17542 |
| **07/21** | $18077 | $15704 | $17884 |
| **08/21** | $18505 | $15981 | $18334 |
| **09/21** | $17664 | $15517 | $17592 |
| **10/21** | $18301 | $15899 | $17957 |
| **11/21** | $17557 | $15159 | $17165 |
| **12/21** | $18319 | $15935 | $17722 |
| **01/22** | $15831 | $15165 | $15608 |
| **02/22** | $15110 | $14897 | $15320 |
| **03/22** | $14873 | $14993 | $15367 |
| **04/22** | $13381 | $14023 | $14053 |
| **05/22** | $13156 | $14128 | $13845 |
| **06/22** | $11717 | $12817 | $12397 |
| **07/22** | $12856 | $13456 | $13366 |
| **08/22** | $11955 | $12817 | $12634 |
| **09/22** | $10403 | $11618 | $11208 |
| **10/22** | $10969 | $12242 | $11694 |
| **11/22** | $12499 | $13621 | $12903 |
| **12/22** | $12159 | $13632 | $12815 |
| **01/23** | $13417 | $14736 | $13846 |
| **02/23** | $13105 | $14429 | $13475 |
| **03/23** | $13513 | $14786 | $13801 |
| **04/23** | $13660 | $15204 | $14045 |
| **05/23** | $13366 | $14560 | $13607 |
| **06/23** | $13796 | $15223 | $13890 |
| **07/23** | $14136 | $15715 | $14414 |
| **08/23** | $13553 | $15113 | $13847 |
| **09/23** | $12629 | $14597 | $13038 |
| **10/23** | $11955 | $14005 | $12208 |
| **11/23** | $13451 | $15305 | $13638 |
| **12/23** | $14539 | $16118 | $14642 |
| **01/24** | $13893 | $16211 | $14421 |
| **02/24** | $14272 | $16508 | $14758 |
| **03/24** | $14652 | $17051 | $15097 |
| **04/24** | $13921 | $16614 | $14427 |
| **05/24** | $14782 | $17258 | $14983 |
| **06/24** | $14724 | $16979 | $14684 |
| **07/24** | $15024 | $17477 | $15280 |
| **08/24** | $15559 | $18046 | $15785 |
| **09/24** | $15870 | $18212 | $16187 |
| **10/24** | $14483 | $17222 | $15121 |
| **11/24** | $14465 | $17124 | $15261 |
| **12/24** | $13838 | $16735 | $14870 |
| **01/25** | $14611 | $17614 | $15482 |
| **02/25** | $14317 | $17956 | $15390 |
| **03/25** | $13641 | $17883 | $15233 |
| **04/25** | $14643 | $18702 | $16204 |
| **05/25** | $15479 | $19558 | $17188 |
| **06/25** | $16211 | $19989 | $17858 |
| **07/25** | $15616 | $19708 | $17648 |
| **08/25** | $15792 | $20549 | $18263 |
| **09/25** | $15930 | $20942 | $18538 |
| **10/25** | $15733 | $21188 | $18478 |
| **11/25** | $15445 | $21320 | $18303 |
| **12/25** | $15549 | $21959 | $18583 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class S<sup>Footnote Reference(a)</sup><sup>Footnote Reference(b)</sup> | 12.36 | (0.85) | 4.51 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE SMID Cap Growth Index (Net) | 24.96 | 2.45 | 6.39 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The returns shown for periods prior to October 2, 2024 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. |
| &nbsp;&nbsp;Footnote<sup>(b)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $805895861 |
| **Total number of portfolio holdings** | 71 |
| **Management services fees (represents 0.86% of Fund average net assets)** | $7533596 |
| **Portfolio turnover for the reporting period** | 25% |

---

Columbia Acorn International<sup>®</sup> \| Class S **\|** ASR111_16_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 39.2% |
| United Kingdom | 16.1% |
| Germany | 6.4% |
| Switzerland | 5.1% |
| Sweden | 4.7% |
| United States | 3.8% |
| Finland | 3.7% |
| Italy | 3.3% |
| France | 2.9% |
| Australia | 2.7% |
| Other | 12.3% |

---

### Top Holdings

---

| | |
|:---|:---|
| Taisei Corp. | 3.0% |
| Halma PLC | 2.7% |
| Niterra Co., Ltd. | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Kokusai Electric Corp. | 2.4% |
| Capcom Co., Ltd. | 2.4% |
| Prysmian SpA | 2.4% |
| Hexagon AB, Class B | 2.2% |
| Fisher & Paykel Healthcare Corp., Ltd. | 2.2% |
| Babcock International Group PLC | 2.2% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 31.0% |
| Information Technology | 22.3% |
| Communication Services | 9.3% |
| Financials | 9.2% |
| Health Care | 5.9% |
| Consumer Discretionary | 5.3% |
| Materials | 5.0% |
| Consumer Staples | 4.9% |
| Real Estate | 4.0% |
| Energy | 2.9% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International<sup>®</sup> \| Class S **\|** ASR111_16_(02/26) \|

# Columbia Acorn International<sup>®</sup>
Institutional 2 Class \| CAIRX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International<sup>®</sup> (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 2 Class | $96 | 0.90% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 2 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and information technology sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A smaller allocation to the consumer discretionary sector buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Bank of Ireland, an Irish diversified financial services company; BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer; and Simplex Holdings, a Japanese system development and financial solutions provider, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, communication services, consumer staples, health care and materials sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the communication services and real estate sectors and small allocations to the industrials and materials sectors detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Silergy Corp., a Taiwanese manufacturer of power management integrated circuits; Interparfums, a perfume and fragrance manufacturer; IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Amplifon SpA, an Italian maker of customized hearing solutions; and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International<sup>®</sup> \| Institutional 2 Class **\|** ASR111_15_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 2 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g07q53.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International<sup>®</sup> Institutional 2 Class ($15632)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE SMID Cap Growth Index (Net) ($18583)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9476 | $9277 | $9249 |
| **02/16** | $9373 | $9107 | $9207 |
| **03/16** | $10015 | $9699 | $9908 |
| **04/16** | $10064 | $9980 | $10071 |
| **05/16** | $10097 | $9890 | $10123 |
| **06/16** | $9874 | $9558 | $9712 |
| **07/16** | $10350 | $10042 | $10271 |
| **08/16** | $10425 | $10049 | $10129 |
| **09/16** | $10690 | $10173 | $10363 |
| **10/16** | $10177 | $9965 | $9941 |
| **11/16** | $9714 | $9766 | $9627 |
| **12/16** | $9777 | $10100 | $9827 |
| **01/17** | $10187 | $10393 | $10233 |
| **02/17** | $10407 | $10542 | $10418 |
| **03/17** | $10728 | $10832 | $10673 |
| **04/17** | $11211 | $11107 | $11103 |
| **05/17** | $11638 | $11515 | $11609 |
| **06/17** | $11594 | $11495 | $11556 |
| **07/17** | $11902 | $11826 | $11921 |
| **08/17** | $11892 | $11822 | $12030 |
| **09/17** | $12161 | $12116 | $12360 |
| **10/17** | $12404 | $12300 | $12653 |
| **11/17** | $12661 | $12429 | $12813 |
| **12/17** | $12932 | $12628 | $13084 |
| **01/18** | $13622 | $13262 | $13775 |
| **02/18** | $13094 | $12663 | $13256 |
| **03/18** | $13221 | $12435 | $13070 |
| **04/18** | $13219 | $12719 | $13192 |
| **05/18** | $13196 | $12433 | $13228 |
| **06/18** | $12947 | $12281 | $13032 |
| **07/18** | $13117 | $12584 | $13180 |
| **08/18** | $13013 | $12341 | $13139 |
| **09/18** | $12907 | $12448 | $13010 |
| **10/18** | $11516 | $11457 | $11634 |
| **11/18** | $11541 | $11442 | $11482 |
| **12/18** | $10882 | $10887 | $10806 |
| **01/19** | $11805 | $11602 | $11619 |
| **02/19** | $12163 | $11898 | $11943 |
| **03/19** | $12244 | $11973 | $12041 |
| **04/19** | $12735 | $12310 | $12469 |
| **05/19** | $12192 | $11719 | $11849 |
| **06/19** | $12900 | $12414 | $12482 |
| **07/19** | $12656 | $12256 | $12440 |
| **08/19** | $12452 | $11939 | $12181 |
| **09/19** | $12499 | $12281 | $12384 |
| **10/19** | $13147 | $12722 | $12896 |
| **11/19** | $13579 | $12866 | $13260 |
| **12/19** | $14141 | $13284 | $13726 |
| **01/20** | $13674 | $13006 | $13497 |
| **02/20** | $12554 | $11831 | $12252 |
| **03/20** | $10112 | $10252 | $10568 |
| **04/20** | $11327 | $10914 | $11675 |
| **05/20** | $12480 | $11389 | $12666 |
| **06/20** | $12873 | $11777 | $12935 |
| **07/20** | $13565 | $12051 | $13555 |
| **08/20** | $14239 | $12671 | $14425 |
| **09/20** | $14274 | $12342 | $14406 |
| **10/20** | $13848 | $11849 | $13944 |
| **11/20** | $15122 | $13686 | $15562 |
| **12/20** | $16271 | $14322 | $16468 |
| **01/21** | $16319 | $14169 | $16344 |
| **02/21** | $16257 | $14487 | $16247 |
| **03/21** | $16257 | $14820 | $16455 |
| **04/21** | $17315 | $15266 | $17236 |
| **05/21** | $17598 | $15764 | $17564 |
| **06/21** | $17640 | $15587 | $17542 |
| **07/21** | $18137 | $15704 | $17884 |
| **08/21** | $18562 | $15981 | $18334 |
| **09/21** | $17723 | $15517 | $17592 |
| **10/21** | $18362 | $15899 | $17957 |
| **11/21** | $17615 | $15159 | $17165 |
| **12/21** | $18382 | $15935 | $17722 |
| **01/22** | $15883 | $15165 | $15608 |
| **02/22** | $15164 | $14897 | $15320 |
| **03/22** | $14921 | $14993 | $15367 |
| **04/22** | $13428 | $14023 | $14053 |
| **05/22** | $13207 | $14128 | $13845 |
| **06/22** | $11762 | $12817 | $12397 |
| **07/22** | $12906 | $13456 | $13366 |
| **08/22** | $12001 | $12817 | $12634 |
| **09/22** | $10442 | $11618 | $11208 |
| **10/22** | $11011 | $12242 | $11694 |
| **11/22** | $12548 | $13621 | $12903 |
| **12/22** | $12206 | $13632 | $12815 |
| **01/23** | $13470 | $14736 | $13846 |
| **02/23** | $13162 | $14429 | $13475 |
| **03/23** | $13566 | $14786 | $13801 |
| **04/23** | $13714 | $15204 | $14045 |
| **05/23** | $13424 | $14560 | $13607 |
| **06/23** | $13856 | $15223 | $13890 |
| **07/23** | $14198 | $15715 | $14414 |
| **08/23** | $13612 | $15113 | $13847 |
| **09/23** | $12684 | $14597 | $13038 |
| **10/23** | $12007 | $14005 | $12208 |
| **11/23** | $13509 | $15305 | $13638 |
| **12/23** | $14602 | $16118 | $14642 |
| **01/24** | $13953 | $16211 | $14421 |
| **02/24** | $14334 | $16508 | $14758 |
| **03/24** | $14716 | $17051 | $15097 |
| **04/24** | $13982 | $16614 | $14427 |
| **05/24** | $14852 | $17258 | $14983 |
| **06/24** | $14792 | $16979 | $14684 |
| **07/24** | $15099 | $17477 | $15280 |
| **08/24** | $15636 | $18046 | $15785 |
| **09/24** | $15943 | $18212 | $16187 |
| **10/24** | $14555 | $17222 | $15121 |
| **11/24** | $14538 | $17124 | $15261 |
| **12/24** | $13903 | $16735 | $14870 |
| **01/25** | $14679 | $17614 | $15482 |
| **02/25** | $14391 | $17956 | $15390 |
| **03/25** | $13710 | $17883 | $15233 |
| **04/25** | $14718 | $18702 | $16204 |
| **05/25** | $15559 | $19558 | $17188 |
| **06/25** | $16295 | $19989 | $17858 |
| **07/25** | $15696 | $19708 | $17648 |
| **08/25** | $15874 | $20549 | $18263 |
| **09/25** | $16019 | $20942 | $18538 |
| **10/25** | $15821 | $21188 | $18478 |
| **11/25** | $15532 | $21320 | $18303 |
| **12/25** | $15632 | $21959 | $18583 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 2 Class<sup>Footnote Reference(a)</sup> | 12.44 | (0.80) | 4.57 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE SMID Cap Growth Index (Net) | 24.96 | 2.45 | 6.39 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $805895861 |
| **Total number of portfolio holdings** | 71 |
| **Management services fees (represents 0.86% of Fund average net assets)** | $7533596 |
| **Portfolio turnover for the reporting period** | 25% |

---

Columbia Acorn International<sup>®</sup> \| Institutional 2 Class **\|** ASR111_15_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 39.2% |
| United Kingdom | 16.1% |
| Germany | 6.4% |
| Switzerland | 5.1% |
| Sweden | 4.7% |
| United States | 3.8% |
| Finland | 3.7% |
| Italy | 3.3% |
| France | 2.9% |
| Australia | 2.7% |
| Other | 12.3% |

---

### Top Holdings

---

| | |
|:---|:---|
| Taisei Corp. | 3.0% |
| Halma PLC | 2.7% |
| Niterra Co., Ltd. | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Kokusai Electric Corp. | 2.4% |
| Capcom Co., Ltd. | 2.4% |
| Prysmian SpA | 2.4% |
| Hexagon AB, Class B | 2.2% |
| Fisher & Paykel Healthcare Corp., Ltd. | 2.2% |
| Babcock International Group PLC | 2.2% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 31.0% |
| Information Technology | 22.3% |
| Communication Services | 9.3% |
| Financials | 9.2% |
| Health Care | 5.9% |
| Consumer Discretionary | 5.3% |
| Materials | 5.0% |
| Consumer Staples | 4.9% |
| Real Estate | 4.0% |
| Energy | 2.9% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International<sup>®</sup> \| Institutional 2 Class **\|** ASR111_15_(02/26) \|

# Columbia Acorn International<sup>®</sup>
Institutional 3 Class \| CCYIX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International<sup>®</sup> (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 3 Class | $90 | 0.85% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 3 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and information technology sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A smaller allocation to the consumer discretionary sector buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Bank of Ireland, an Irish diversified financial services company; BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer; and Simplex Holdings, a Japanese system development and financial solutions provider, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, communication services, consumer staples, health care and materials sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the communication services and real estate sectors and small allocations to the industrials and materials sectors detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Silergy Corp., a Taiwanese manufacturer of power management integrated circuits; Interparfums, a perfume and fragrance manufacturer; IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Amplifon SpA, an Italian maker of customized hearing solutions; and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International<sup>®</sup> \| Institutional 3 Class **\|** ASR111_17_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 3 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g58x41.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International<sup>®</sup> Institutional 3 Class ($15703)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE SMID Cap Growth Index (Net) ($18583)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9477 | $9277 | $9249 |
| **02/16** | $9373 | $9107 | $9207 |
| **03/16** | $10015 | $9699 | $9908 |
| **04/16** | $10066 | $9980 | $10071 |
| **05/16** | $10101 | $9890 | $10123 |
| **06/16** | $9877 | $9558 | $9712 |
| **07/16** | $10352 | $10042 | $10271 |
| **08/16** | $10429 | $10049 | $10129 |
| **09/16** | $10692 | $10173 | $10363 |
| **10/16** | $10181 | $9965 | $9941 |
| **11/16** | $9719 | $9766 | $9627 |
| **12/16** | $9781 | $10100 | $9827 |
| **01/17** | $10193 | $10393 | $10233 |
| **02/17** | $10414 | $10542 | $10418 |
| **03/17** | $10736 | $10832 | $10673 |
| **04/17** | $11217 | $11107 | $11103 |
| **05/17** | $11647 | $11515 | $11609 |
| **06/17** | $11603 | $11495 | $11556 |
| **07/17** | $11911 | $11826 | $11921 |
| **08/17** | $11901 | $11822 | $12030 |
| **09/17** | $12171 | $12116 | $12360 |
| **10/17** | $12417 | $12300 | $12653 |
| **11/17** | $12674 | $12429 | $12813 |
| **12/17** | $12946 | $12628 | $13084 |
| **01/18** | $13635 | $13262 | $13775 |
| **02/18** | $13109 | $12663 | $13256 |
| **03/18** | $13236 | $12435 | $13070 |
| **04/18** | $13236 | $12719 | $13192 |
| **05/18** | $13214 | $12433 | $13228 |
| **06/18** | $12963 | $12281 | $13032 |
| **07/18** | $13134 | $12584 | $13180 |
| **08/18** | $13032 | $12341 | $13139 |
| **09/18** | $12923 | $12448 | $13010 |
| **10/18** | $11532 | $11457 | $11634 |
| **11/18** | $11557 | $11442 | $11482 |
| **12/18** | $10899 | $10887 | $10806 |
| **01/19** | $11823 | $11602 | $11619 |
| **02/19** | $12185 | $11898 | $11943 |
| **03/19** | $12265 | $11973 | $12041 |
| **04/19** | $12758 | $12310 | $12469 |
| **05/19** | $12214 | $11719 | $11849 |
| **06/19** | $12925 | $12414 | $12482 |
| **07/19** | $12681 | $12256 | $12440 |
| **08/19** | $12475 | $11939 | $12181 |
| **09/19** | $12521 | $12281 | $12384 |
| **10/19** | $13174 | $12722 | $12896 |
| **11/19** | $13609 | $12866 | $13260 |
| **12/19** | $14172 | $13284 | $13726 |
| **01/20** | $13702 | $13006 | $13497 |
| **02/20** | $12582 | $11831 | $12252 |
| **03/20** | $10133 | $10252 | $10568 |
| **04/20** | $11352 | $10914 | $11675 |
| **05/20** | $12508 | $11389 | $12666 |
| **06/20** | $12906 | $11777 | $12935 |
| **07/20** | $13598 | $12051 | $13555 |
| **08/20** | $14273 | $12671 | $14425 |
| **09/20** | $14312 | $12342 | $14406 |
| **10/20** | $13882 | $11849 | $13944 |
| **11/20** | $15159 | $13686 | $15562 |
| **12/20** | $16312 | $14322 | $16468 |
| **01/21** | $16359 | $14169 | $16344 |
| **02/21** | $16298 | $14487 | $16247 |
| **03/21** | $16298 | $14820 | $16455 |
| **04/21** | $17357 | $15266 | $17236 |
| **05/21** | $17646 | $15764 | $17564 |
| **06/21** | $17688 | $15587 | $17542 |
| **07/21** | $18184 | $15704 | $17884 |
| **08/21** | $18613 | $15981 | $18334 |
| **09/21** | $17770 | $15517 | $17592 |
| **10/21** | $18410 | $15899 | $17957 |
| **11/21** | $17664 | $15159 | $17165 |
| **12/21** | $18433 | $15935 | $17722 |
| **01/22** | $15926 | $15165 | $15608 |
| **02/22** | $15207 | $14897 | $15320 |
| **03/22** | $14967 | $14993 | $15367 |
| **04/22** | $13469 | $14023 | $14053 |
| **05/22** | $13245 | $14128 | $13845 |
| **06/22** | $11800 | $12817 | $12397 |
| **07/22** | $12943 | $13456 | $13366 |
| **08/22** | $12041 | $12817 | $12634 |
| **09/22** | $10477 | $11618 | $11208 |
| **10/22** | $11043 | $12242 | $11694 |
| **11/22** | $12590 | $13621 | $12903 |
| **12/22** | $12243 | $13632 | $12815 |
| **01/23** | $13515 | $14736 | $13846 |
| **02/23** | $13201 | $14429 | $13475 |
| **03/23** | $13610 | $14786 | $13801 |
| **04/23** | $13762 | $15204 | $14045 |
| **05/23** | $13470 | $14560 | $13607 |
| **06/23** | $13902 | $15223 | $13890 |
| **07/23** | $14244 | $15715 | $14414 |
| **08/23** | $13661 | $15113 | $13847 |
| **09/23** | $12730 | $14597 | $13038 |
| **10/23** | $12052 | $14005 | $12208 |
| **11/23** | $13554 | $15305 | $13638 |
| **12/23** | $14659 | $16118 | $14642 |
| **01/24** | $14008 | $16211 | $14421 |
| **02/24** | $14390 | $16508 | $14758 |
| **03/24** | $14776 | $17051 | $15097 |
| **04/24** | $14036 | $16614 | $14427 |
| **05/24** | $14911 | $17258 | $14983 |
| **06/24** | $14849 | $16979 | $14684 |
| **07/24** | $15158 | $17477 | $15280 |
| **08/24** | $15698 | $18046 | $15785 |
| **09/24** | $16013 | $18212 | $16187 |
| **10/24** | $14617 | $17222 | $15121 |
| **11/24** | $14593 | $17124 | $15261 |
| **12/24** | $13963 | $16735 | $14870 |
| **01/25** | $14739 | $17614 | $15482 |
| **02/25** | $14449 | $17956 | $15390 |
| **03/25** | $13767 | $17883 | $15233 |
| **04/25** | $14784 | $18702 | $16204 |
| **05/25** | $15623 | $19558 | $17188 |
| **06/25** | $16367 | $19989 | $17858 |
| **07/25** | $15765 | $19708 | $17648 |
| **08/25** | $15946 | $20549 | $18263 |
| **09/25** | $16088 | $20942 | $18538 |
| **10/25** | $15888 | $21188 | $18478 |
| **11/25** | $15603 | $21320 | $18303 |
| **12/25** | $15703 | $21959 | $18583 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 3 Class<sup>Footnote Reference(a)</sup> | 12.46 | (0.76) | 4.62 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE SMID Cap Growth Index (Net) | 24.96 | 2.45 | 6.39 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $805895861 |
| **Total number of portfolio holdings** | 71 |
| **Management services fees (represents 0.86% of Fund average net assets)** | $7533596 |
| **Portfolio turnover for the reporting period** | 25% |

---

Columbia Acorn International<sup>®</sup> \| Institutional 3 Class **\|** ASR111_17_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 39.2% |
| United Kingdom | 16.1% |
| Germany | 6.4% |
| Switzerland | 5.1% |
| Sweden | 4.7% |
| United States | 3.8% |
| Finland | 3.7% |
| Italy | 3.3% |
| France | 2.9% |
| Australia | 2.7% |
| Other | 12.3% |

---

### Top Holdings

---

| | |
|:---|:---|
| Taisei Corp. | 3.0% |
| Halma PLC | 2.7% |
| Niterra Co., Ltd. | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Kokusai Electric Corp. | 2.4% |
| Capcom Co., Ltd. | 2.4% |
| Prysmian SpA | 2.4% |
| Hexagon AB, Class B | 2.2% |
| Fisher & Paykel Healthcare Corp., Ltd. | 2.2% |
| Babcock International Group PLC | 2.2% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 31.0% |
| Information Technology | 22.3% |
| Communication Services | 9.3% |
| Financials | 9.2% |
| Health Care | 5.9% |
| Consumer Discretionary | 5.3% |
| Materials | 5.0% |
| Consumer Staples | 4.9% |
| Real Estate | 4.0% |
| Energy | 2.9% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International<sup>®</sup> \| Institutional 3 Class **\|** ASR111_17_(02/26) \|

# Columbia Acorn International<sup>®</sup>
Institutional Class \| ACINX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International<sup>®</sup> (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional Class | $102 | 0.96% |

---

## Management's Discussion of Fund Performance
The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials and information technology sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| A smaller allocation to the consumer discretionary sector buoyed the Fund's relative performance during the annual period.

**Individual holdings** \| Positions in Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Bank of Ireland, an Irish diversified financial services company; BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer; and Simplex Holdings, a Japanese system development and financial solutions provider, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, communication services, consumer staples, health care and materials sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the communication services and real estate sectors and small allocations to the industrials and materials sectors detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in Silergy Corp., a Taiwanese manufacturer of power management integrated circuits; Interparfums, a perfume and fragrance manufacturer; IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Amplifon SpA, an Italian maker of customized hearing solutions; and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International<sup>®</sup> \| Institutional Class **\|** ASR111_08_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g98x21.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International<sup>®</sup> Institutional Class ($15549)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE SMID Cap Growth Index (Net) ($18583)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9476 | $9277 | $9249 |
| **02/16** | $9371 | $9107 | $9207 |
| **03/16** | $10013 | $9699 | $9908 |
| **04/16** | $10061 | $9980 | $10071 |
| **05/16** | $10095 | $9890 | $10123 |
| **06/16** | $9871 | $9558 | $9712 |
| **07/16** | $10347 | $10042 | $10271 |
| **08/16** | $10419 | $10049 | $10129 |
| **09/16** | $10684 | $10173 | $10363 |
| **10/16** | $10172 | $9965 | $9941 |
| **11/16** | $9712 | $9766 | $9627 |
| **12/16** | $9772 | $10100 | $9827 |
| **01/17** | $10181 | $10393 | $10233 |
| **02/17** | $10401 | $10542 | $10418 |
| **03/17** | $10723 | $10832 | $10673 |
| **04/17** | $11204 | $11107 | $11103 |
| **05/17** | $11631 | $11515 | $11609 |
| **06/17** | $11587 | $11495 | $11556 |
| **07/17** | $11895 | $11826 | $11921 |
| **08/17** | $11882 | $11822 | $12030 |
| **09/17** | $12151 | $12116 | $12360 |
| **10/17** | $12394 | $12300 | $12653 |
| **11/17** | $12650 | $12429 | $12813 |
| **12/17** | $12922 | $12628 | $13084 |
| **01/18** | $13608 | $13262 | $13775 |
| **02/18** | $13081 | $12663 | $13256 |
| **03/18** | $13205 | $12435 | $13070 |
| **04/18** | $13203 | $12719 | $13192 |
| **05/18** | $13180 | $12433 | $13228 |
| **06/18** | $12931 | $12281 | $13032 |
| **07/18** | $13101 | $12584 | $13180 |
| **08/18** | $12997 | $12341 | $13139 |
| **09/18** | $12888 | $12448 | $13010 |
| **10/18** | $11499 | $11457 | $11634 |
| **11/18** | $11522 | $11442 | $11482 |
| **12/18** | $10865 | $10887 | $10806 |
| **01/19** | $11785 | $11602 | $11619 |
| **02/19** | $12142 | $11898 | $11943 |
| **03/19** | $12223 | $11973 | $12041 |
| **04/19** | $12713 | $12310 | $12469 |
| **05/19** | $12168 | $11719 | $11849 |
| **06/19** | $12877 | $12414 | $12482 |
| **07/19** | $12630 | $12256 | $12440 |
| **08/19** | $12427 | $11939 | $12181 |
| **09/19** | $12474 | $12281 | $12384 |
| **10/19** | $13120 | $12722 | $12896 |
| **11/19** | $13551 | $12866 | $13260 |
| **12/19** | $14112 | $13284 | $13726 |
| **01/20** | $13647 | $13006 | $13497 |
| **02/20** | $12530 | $11831 | $12252 |
| **03/20** | $10091 | $10252 | $10568 |
| **04/20** | $11302 | $10914 | $11675 |
| **05/20** | $12452 | $11389 | $12666 |
| **06/20** | $12844 | $11777 | $12935 |
| **07/20** | $13533 | $12051 | $13555 |
| **08/20** | $14201 | $12671 | $14425 |
| **09/20** | $14240 | $12342 | $14406 |
| **10/20** | $13811 | $11849 | $13944 |
| **11/20** | $15081 | $13686 | $15562 |
| **12/20** | $16227 | $14322 | $16468 |
| **01/21** | $16275 | $14169 | $16344 |
| **02/21** | $16209 | $14487 | $16247 |
| **03/21** | $16209 | $14820 | $16455 |
| **04/21** | $17263 | $15266 | $17236 |
| **05/21** | $17546 | $15764 | $17564 |
| **06/21** | $17586 | $15587 | $17542 |
| **07/21** | $18077 | $15704 | $17884 |
| **08/21** | $18505 | $15981 | $18334 |
| **09/21** | $17664 | $15517 | $17592 |
| **10/21** | $18301 | $15899 | $17957 |
| **11/21** | $17557 | $15159 | $17165 |
| **12/21** | $18319 | $15935 | $17722 |
| **01/22** | $15831 | $15165 | $15608 |
| **02/22** | $15110 | $14897 | $15320 |
| **03/22** | $14873 | $14993 | $15367 |
| **04/22** | $13381 | $14023 | $14053 |
| **05/22** | $13156 | $14128 | $13845 |
| **06/22** | $11717 | $12817 | $12397 |
| **07/22** | $12856 | $13456 | $13366 |
| **08/22** | $11955 | $12817 | $12634 |
| **09/22** | $10403 | $11618 | $11208 |
| **10/22** | $10969 | $12242 | $11694 |
| **11/22** | $12499 | $13621 | $12903 |
| **12/22** | $12159 | $13632 | $12815 |
| **01/23** | $13417 | $14736 | $13846 |
| **02/23** | $13105 | $14429 | $13475 |
| **03/23** | $13513 | $14786 | $13801 |
| **04/23** | $13660 | $15204 | $14045 |
| **05/23** | $13366 | $14560 | $13607 |
| **06/23** | $13796 | $15223 | $13890 |
| **07/23** | $14136 | $15715 | $14414 |
| **08/23** | $13553 | $15113 | $13847 |
| **09/23** | $12629 | $14597 | $13038 |
| **10/23** | $11955 | $14005 | $12208 |
| **11/23** | $13451 | $15305 | $13638 |
| **12/23** | $14539 | $16118 | $14642 |
| **01/24** | $13893 | $16211 | $14421 |
| **02/24** | $14272 | $16508 | $14758 |
| **03/24** | $14652 | $17051 | $15097 |
| **04/24** | $13921 | $16614 | $14427 |
| **05/24** | $14782 | $17258 | $14983 |
| **06/24** | $14724 | $16979 | $14684 |
| **07/24** | $15024 | $17477 | $15280 |
| **08/24** | $15559 | $18046 | $15785 |
| **09/24** | $15870 | $18212 | $16187 |
| **10/24** | $14483 | $17222 | $15121 |
| **11/24** | $14465 | $17124 | $15261 |
| **12/24** | $13838 | $16735 | $14870 |
| **01/25** | $14604 | $17614 | $15482 |
| **02/25** | $14317 | $17956 | $15390 |
| **03/25** | $13641 | $17883 | $15233 |
| **04/25** | $14643 | $18702 | $16204 |
| **05/25** | $15479 | $19558 | $17188 |
| **06/25** | $16211 | $19989 | $17858 |
| **07/25** | $15616 | $19708 | $17648 |
| **08/25** | $15792 | $20549 | $18263 |
| **09/25** | $15930 | $20942 | $18538 |
| **10/25** | $15733 | $21188 | $18478 |
| **11/25** | $15445 | $21320 | $18303 |
| **12/25** | $15549 | $21959 | $18583 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional Class<sup>Footnote Reference(a)</sup> | 12.36 | (0.85) | 4.51 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE SMID Cap Growth Index (Net) | 24.96 | 2.45 | 6.39 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $805895861 |
| **Total number of portfolio holdings** | 71 |
| **Management services fees (represents 0.86% of Fund average net assets)** | $7533596 |
| **Portfolio turnover for the reporting period** | 25% |

---

Columbia Acorn International<sup>®</sup> \| Institutional Class **\|** ASR111_08_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 39.2% |
| United Kingdom | 16.1% |
| Germany | 6.4% |
| Switzerland | 5.1% |
| Sweden | 4.7% |
| United States | 3.8% |
| Finland | 3.7% |
| Italy | 3.3% |
| France | 2.9% |
| Australia | 2.7% |
| Other | 12.3% |

---

### Top Holdings

---

| | |
|:---|:---|
| Taisei Corp. | 3.0% |
| Halma PLC | 2.7% |
| Niterra Co., Ltd. | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Kokusai Electric Corp. | 2.4% |
| Capcom Co., Ltd. | 2.4% |
| Prysmian SpA | 2.4% |
| Hexagon AB, Class B | 2.2% |
| Fisher & Paykel Healthcare Corp., Ltd. | 2.2% |
| Babcock International Group PLC | 2.2% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 31.0% |
| Information Technology | 22.3% |
| Communication Services | 9.3% |
| Financials | 9.2% |
| Health Care | 5.9% |
| Consumer Discretionary | 5.3% |
| Materials | 5.0% |
| Consumer Staples | 4.9% |
| Real Estate | 4.0% |
| Energy | 2.9% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International<sup>®</sup> \| Institutional Class **\|** ASR111_08_(02/26) \|

# Columbia Acorn International Select℠
Class A \| LAFAX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International Select℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class A | $123 | 1.12% |

---

## Management's Discussion of Fund Performance
The performance of Class A shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials, information technology, consumer discretionary, materials and consumer staples sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the communication services and financials sectors and smaller allocations to the health care and consumer discretionary sectors buoyed the Fund relative performance during the annual period.

**Individual holdings** \| Positions in Bank of Ireland, an Irish diversified financial services company; Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Standard Chartered, a London-based provider of banking and financial services; and BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, health care and communication services sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the consumer staples and real estate sectors and a small allocation to the industrials sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in adidas, a German manufacturer of athletic and lifestyle products; OMRON Corporation, a Japanese maker of automation components, equipment, and system IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Rolls-Royce Holdings, a London-based manufacturer of integrated power systems for use in the air, on land, and at sea, and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International Select℠ \| Class A **\|** ASR112_01_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g76f90.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International Select℠ Class A (including sales charges) ($17573)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE Growth Index (Net) ($20466)** |
| **12/15** | $9426 | $10000 | $10000 |
| **01/16** | $8953 | $9277 | $9364 |
| **02/16** | $8767 | $9107 | $9201 |
| **03/16** | $9236 | $9699 | $9793 |
| **04/16** | $9280 | $9980 | $9979 |
| **05/16** | $9337 | $9890 | $9954 |
| **06/16** | $9249 | $9558 | $9778 |
| **07/16** | $9673 | $10042 | $10256 |
| **08/16** | $9881 | $10049 | $10112 |
| **09/16** | $10239 | $10173 | $10263 |
| **10/16** | $9730 | $9965 | $9821 |
| **11/16** | $9328 | $9766 | $9486 |
| **12/16** | $9511 | $10100 | $9696 |
| **01/17** | $10009 | $10393 | $10022 |
| **02/17** | $10227 | $10542 | $10244 |
| **03/17** | $10557 | $10832 | $10522 |
| **04/17** | $11065 | $11107 | $10838 |
| **05/17** | $11385 | $11515 | $11387 |
| **06/17** | $11425 | $11495 | $11313 |
| **07/17** | $11893 | $11826 | $11587 |
| **08/17** | $11897 | $11822 | $11652 |
| **09/17** | $12053 | $12116 | $11872 |
| **10/17** | $12454 | $12300 | $12142 |
| **11/17** | $12699 | $12429 | $12288 |
| **12/17** | $12868 | $12628 | $12494 |
| **01/18** | $13447 | $13262 | $13073 |
| **02/18** | $12922 | $12663 | $12514 |
| **03/18** | $12930 | $12435 | $12364 |
| **04/18** | $12913 | $12719 | $12550 |
| **05/18** | $13055 | $12433 | $12525 |
| **06/18** | $13100 | $12281 | $12377 |
| **07/18** | $13407 | $12584 | $12633 |
| **08/18** | $13411 | $12341 | $12598 |
| **09/18** | $13394 | $12448 | $12566 |
| **10/18** | $12053 | $11457 | $11409 |
| **11/18** | $11915 | $11442 | $11443 |
| **12/18** | $11265 | $10887 | $10891 |
| **01/19** | $12259 | $11602 | $11593 |
| **02/19** | $12639 | $11898 | $11992 |
| **03/19** | $13019 | $11973 | $12203 |
| **04/19** | $13682 | $12310 | $12602 |
| **05/19** | $12980 | $11719 | $12115 |
| **06/19** | $13880 | $12414 | $12902 |
| **07/19** | $13540 | $12256 | $12855 |
| **08/19** | $13443 | $11939 | $12699 |
| **09/19** | $13452 | $12281 | $12844 |
| **10/19** | $13982 | $12722 | $13304 |
| **11/19** | $14434 | $12866 | $13543 |
| **12/19** | $15024 | $13284 | $13930 |
| **01/20** | $14756 | $13006 | $13850 |
| **02/20** | $13662 | $11831 | $12654 |
| **03/20** | $11165 | $10252 | $11490 |
| **04/20** | $12411 | $10914 | $12342 |
| **05/20** | $13673 | $11389 | $13016 |
| **06/20** | $14079 | $11777 | $13438 |
| **07/20** | $14965 | $12051 | $14041 |
| **08/20** | $15698 | $12671 | $14666 |
| **09/20** | $15682 | $12342 | $14570 |
| **10/20** | $15218 | $11849 | $13993 |
| **11/20** | $16674 | $13686 | $15712 |
| **12/20** | $17760 | $14322 | $16478 |
| **01/21** | $17428 | $14169 | $16254 |
| **02/21** | $17101 | $14487 | $16198 |
| **03/21** | $17059 | $14820 | $16385 |
| **04/21** | $18441 | $15266 | $17075 |
| **05/21** | $18568 | $15764 | $17592 |
| **06/21** | $18518 | $15587 | $17600 |
| **07/21** | $19122 | $15704 | $17903 |
| **08/21** | $19768 | $15981 | $18325 |
| **09/21** | $18873 | $15517 | $17612 |
| **10/21** | $19800 | $15899 | $18189 |
| **11/21** | $19127 | $15159 | $17572 |
| **12/21** | $19623 | $15935 | $18332 |
| **01/22** | $16821 | $15165 | $16408 |
| **02/22** | $16317 | $14897 | $16044 |
| **03/22** | $15962 | $14993 | $16143 |
| **04/22** | $14229 | $14023 | $14851 |
| **05/22** | $14207 | $14128 | $14678 |
| **06/22** | $12535 | $12817 | $13418 |
| **07/22** | $13920 | $13456 | $14481 |
| **08/22** | $12678 | $12817 | $13603 |
| **09/22** | $10833 | $11618 | $12278 |
| **10/22** | $11385 | $12242 | $12809 |
| **11/22** | $12977 | $13621 | $14287 |
| **12/22** | $12403 | $13632 | $14126 |
| **01/23** | $13725 | $14736 | $15325 |
| **02/23** | $13322 | $14429 | $14897 |
| **03/23** | $13759 | $14786 | $15693 |
| **04/23** | $13892 | $15204 | $16074 |
| **05/23** | $13713 | $14560 | $15578 |
| **06/23** | $14041 | $15223 | $16128 |
| **07/23** | $14127 | $15715 | $16445 |
| **08/23** | $13501 | $15113 | $15673 |
| **09/23** | $12466 | $14597 | $14734 |
| **10/23** | $11856 | $14005 | $14190 |
| **11/23** | $13702 | $15305 | $15710 |
| **12/23** | $14651 | $16118 | $16609 |
| **01/24** | $14162 | $16211 | $16806 |
| **02/24** | $14576 | $16508 | $17373 |
| **03/24** | $15134 | $17051 | $17777 |
| **04/24** | $14587 | $16614 | $17071 |
| **05/24** | $15421 | $17258 | $17722 |
| **06/24** | $15250 | $16979 | $17643 |
| **07/24** | $15523 | $17477 | $17860 |
| **08/24** | $16010 | $18046 | $18564 |
| **09/24** | $16045 | $18212 | $18645 |
| **10/24** | $14931 | $17222 | $17494 |
| **11/24** | $15245 | $17124 | $17430 |
| **12/24** | $14607 | $16735 | $16948 |
| **01/25** | $15332 | $17614 | $17865 |
| **02/25** | $15477 | $17956 | $17888 |
| **03/25** | $14891 | $17883 | $17310 |
| **04/25** | $15569 | $18702 | $18202 |
| **05/25** | $16132 | $19558 | $19144 |
| **06/25** | $16724 | $19989 | $19653 |
| **07/25** | $16164 | $19708 | $19062 |
| **08/25** | $16581 | $20549 | $19597 |
| **09/25** | $17284 | $20942 | $20092 |
| **10/25** | $17397 | $21188 | $20413 |
| **11/25** | $17194 | $21320 | $20112 |
| **12/25** | $17573 | $21959 | $20466 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class A (excluding sales charges)<sup>Footnote Reference(a)</sup> | 20.31 | (0.21) | 6.43 |
| Class A (including sales charges)<sup>Footnote Reference(a)</sup> | 13.38 | (1.38) | 5.80 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE Growth Index (Net) | 20.76 | 4.43 | 7.42 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $199839273 |
| **Total number of portfolio holdings** | 61 |
| **Management services fees (represents 0.87% of Fund average net assets)** | $1715600 |
| **Portfolio turnover for the reporting period** | 21% |

---

Columbia Acorn International Select℠ \| Class A **\|** ASR112_01_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 27.9% |
| United Kingdom | 21.6% |
| France | 18.1% |
| Germany | 7.6% |
| Switzerland | 5.7% |
| Netherlands | 3.6% |
| United States | 3.5% |
| Spain | 2.8% |
| Ireland | 2.6% |
| Italy | 1.8% |
| Other | 5.2% |

---

### Top Holdings

---

| | |
|:---|:---|
| Schneider Electric SE | 4.1% |
| ASML Holding NV | 3.6% |
| Taisei Corp. | 3.1% |
| LVMH Moet Hennessy Louis Vuitton SE | 3.1% |
| Airbus Group SE | 3.0% |
| 3i Group PLC | 2.9% |
| Industria de Diseno Textil SA | 2.8% |
| Standard Chartered PLC | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Capcom Co., Ltd. | 2.5% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.9% |
| Information Technology | 16.7% |
| Financials | 14.4% |
| Communication Services | 10.6% |
| Consumer Discretionary | 10.2% |
| Health Care | 8.2% |
| Consumer Staples | 6.2% |
| Materials | 3.2% |
| Real Estate | 1.0% |
| Energy | 0.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International Select℠ \| Class A **\|** ASR112_01_(02/26) \|

# Columbia Acorn International Select℠
Class S \| ACFEX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International Select℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class S | $96 | 0.87% |

---

## Management's Discussion of Fund Performance
The performance of Class S shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials, information technology, consumer discretionary, materials and consumer staples sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the communication services and financials sectors and smaller allocations to the health care and consumer discretionary sectors buoyed the Fund relative performance during the annual period.

**Individual holdings** \| Positions in Bank of Ireland, an Irish diversified financial services company; Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Standard Chartered, a London-based provider of banking and financial services; and BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, health care and communication services sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the consumer staples and real estate sectors and a small allocation to the industrials sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in adidas, a German manufacturer of athletic and lifestyle products; OMRON Corporation, a Japanese maker of automation components, equipment, and system IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Rolls-Royce Holdings, a London-based manufacturer of integrated power systems for use in the air, on land, and at sea, and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International Select℠ \| Class S **\|** ASR112_16_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class S shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g13h44.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International Select℠ Class S ($19125)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE Growth Index (Net) ($20466)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9504 | $9277 | $9364 |
| **02/16** | $9310 | $9107 | $9201 |
| **03/16** | $9810 | $9699 | $9793 |
| **04/16** | $9856 | $9980 | $9979 |
| **05/16** | $9926 | $9890 | $9954 |
| **06/16** | $9829 | $9558 | $9778 |
| **07/16** | $10283 | $10042 | $10256 |
| **08/16** | $10505 | $10049 | $10112 |
| **09/16** | $10890 | $10173 | $10263 |
| **10/16** | $10352 | $9965 | $9821 |
| **11/16** | $9926 | $9766 | $9486 |
| **12/16** | $10118 | $10100 | $9696 |
| **01/17** | $10657 | $10393 | $10022 |
| **02/17** | $10891 | $10542 | $10244 |
| **03/17** | $11242 | $10832 | $10522 |
| **04/17** | $11781 | $11107 | $10838 |
| **05/17** | $12127 | $11515 | $11387 |
| **06/17** | $12174 | $11495 | $11313 |
| **07/17** | $12675 | $11826 | $11587 |
| **08/17** | $12680 | $11822 | $11652 |
| **09/17** | $12848 | $12116 | $11872 |
| **10/17** | $13284 | $12300 | $12142 |
| **11/17** | $13546 | $12429 | $12288 |
| **12/17** | $13731 | $12628 | $12494 |
| **01/18** | $14351 | $13262 | $13073 |
| **02/18** | $13792 | $12663 | $12514 |
| **03/18** | $13801 | $12435 | $12364 |
| **04/18** | $13783 | $12719 | $12550 |
| **05/18** | $13942 | $12433 | $12525 |
| **06/18** | $13989 | $12281 | $12377 |
| **07/18** | $14327 | $12584 | $12633 |
| **08/18** | $14332 | $12341 | $12598 |
| **09/18** | $14313 | $12448 | $12566 |
| **10/18** | $12881 | $11457 | $11409 |
| **11/18** | $12740 | $11442 | $11443 |
| **12/18** | $12045 | $10887 | $10891 |
| **01/19** | $13118 | $11602 | $11593 |
| **02/19** | $13523 | $11898 | $11992 |
| **03/19** | $13932 | $11973 | $12203 |
| **04/19** | $14646 | $12310 | $12602 |
| **05/19** | $13897 | $11719 | $12115 |
| **06/19** | $14862 | $12414 | $12902 |
| **07/19** | $14503 | $12256 | $12855 |
| **08/19** | $14401 | $11939 | $12699 |
| **09/19** | $14411 | $12281 | $12844 |
| **10/19** | $14985 | $12722 | $13304 |
| **11/19** | $15472 | $12866 | $13543 |
| **12/19** | $16105 | $13284 | $13930 |
| **01/20** | $15828 | $13006 | $13850 |
| **02/20** | $14656 | $11831 | $12654 |
| **03/20** | $11979 | $10252 | $11490 |
| **04/20** | $13317 | $10914 | $12342 |
| **05/20** | $14672 | $11389 | $13016 |
| **06/20** | $15112 | $11777 | $13438 |
| **07/20** | $16065 | $12051 | $14041 |
| **08/20** | $16856 | $12671 | $14666 |
| **09/20** | $16840 | $12342 | $14570 |
| **10/20** | $16349 | $11849 | $13993 |
| **11/20** | $17915 | $13686 | $15712 |
| **12/20** | $19085 | $14322 | $16478 |
| **01/21** | $18734 | $14169 | $16254 |
| **02/21** | $18389 | $14487 | $16198 |
| **03/21** | $18350 | $14820 | $16385 |
| **04/21** | $19832 | $15266 | $17075 |
| **05/21** | $19977 | $15764 | $17592 |
| **06/21** | $19928 | $15587 | $17600 |
| **07/21** | $20584 | $15704 | $17903 |
| **08/21** | $21279 | $15981 | $18325 |
| **09/21** | $20326 | $15517 | $17612 |
| **10/21** | $21330 | $15899 | $18189 |
| **11/21** | $20601 | $15159 | $17572 |
| **12/21** | $21145 | $15935 | $18332 |
| **01/22** | $18133 | $15165 | $16408 |
| **02/22** | $17587 | $14897 | $16044 |
| **03/22** | $17205 | $14993 | $16143 |
| **04/22** | $15344 | $14023 | $14851 |
| **05/22** | $15326 | $14128 | $14678 |
| **06/22** | $13518 | $12817 | $13418 |
| **07/22** | $15023 | $13456 | $14481 |
| **08/22** | $13683 | $12817 | $13603 |
| **09/22** | $11697 | $11618 | $12278 |
| **10/22** | $12294 | $12242 | $12809 |
| **11/22** | $14018 | $13621 | $14287 |
| **12/22** | $13396 | $13632 | $14126 |
| **01/23** | $14828 | $14736 | $15325 |
| **02/23** | $14395 | $14429 | $14897 |
| **03/23** | $14871 | $14786 | $15693 |
| **04/23** | $15017 | $15204 | $16074 |
| **05/23** | $14828 | $14560 | $15578 |
| **06/23** | $15187 | $15223 | $16128 |
| **07/23** | $15285 | $15715 | $16445 |
| **08/23** | $14602 | $15113 | $15673 |
| **09/23** | $13494 | $14597 | $14734 |
| **10/23** | $12836 | $14005 | $14190 |
| **11/23** | $14834 | $15305 | $15710 |
| **12/23** | $15864 | $16118 | $16609 |
| **01/24** | $15334 | $16211 | $16806 |
| **02/24** | $15796 | $16508 | $17373 |
| **03/24** | $16400 | $17051 | $17777 |
| **04/24** | $15809 | $16614 | $17071 |
| **05/24** | $16716 | $17258 | $17722 |
| **06/24** | $16534 | $16979 | $17643 |
| **07/24** | $16830 | $17477 | $17860 |
| **08/24** | $17366 | $18046 | $18564 |
| **09/24** | $17409 | $18212 | $18645 |
| **10/24** | $16208 | $17222 | $17494 |
| **11/24** | $16547 | $17124 | $17430 |
| **12/24** | $15857 | $16735 | $16948 |
| **01/25** | $16645 | $17614 | $17865 |
| **02/25** | $16811 | $17956 | $17888 |
| **03/25** | $16177 | $17883 | $17310 |
| **04/25** | $16916 | $18702 | $18202 |
| **05/25** | $17532 | $19558 | $19144 |
| **06/25** | $18177 | $19989 | $19653 |
| **07/25** | $17575 | $19708 | $19062 |
| **08/25** | $18031 | $20549 | $19597 |
| **09/25** | $18798 | $20942 | $20092 |
| **10/25** | $18931 | $21188 | $20413 |
| **11/25** | $18709 | $21320 | $20112 |
| **12/25** | $19125 | $21959 | $20466 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class S<sup>Footnote Reference(a)</sup><sup>Footnote Reference(b)</sup> | 20.61 | 0.04 | 6.70 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE Growth Index (Net) | 20.76 | 4.43 | 7.42 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The returns shown for periods prior to October 2, 2024 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. |
| &nbsp;&nbsp;Footnote<sup>(b)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $199839273 |
| **Total number of portfolio holdings** | 61 |
| **Management services fees (represents 0.87% of Fund average net assets)** | $1715600 |
| **Portfolio turnover for the reporting period** | 21% |

---

Columbia Acorn International Select℠ \| Class S **\|** ASR112_16_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 27.9% |
| United Kingdom | 21.6% |
| France | 18.1% |
| Germany | 7.6% |
| Switzerland | 5.7% |
| Netherlands | 3.6% |
| United States | 3.5% |
| Spain | 2.8% |
| Ireland | 2.6% |
| Italy | 1.8% |
| Other | 5.2% |

---

### Top Holdings

---

| | |
|:---|:---|
| Schneider Electric SE | 4.1% |
| ASML Holding NV | 3.6% |
| Taisei Corp. | 3.1% |
| LVMH Moet Hennessy Louis Vuitton SE | 3.1% |
| Airbus Group SE | 3.0% |
| 3i Group PLC | 2.9% |
| Industria de Diseno Textil SA | 2.8% |
| Standard Chartered PLC | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Capcom Co., Ltd. | 2.5% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.9% |
| Information Technology | 16.7% |
| Financials | 14.4% |
| Communication Services | 10.6% |
| Consumer Discretionary | 10.2% |
| Health Care | 8.2% |
| Consumer Staples | 6.2% |
| Materials | 3.2% |
| Real Estate | 1.0% |
| Energy | 0.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International Select℠ \| Class S **\|** ASR112_16_(02/26) \|

# Columbia Acorn International Select℠
Institutional 2 Class \| CRIRX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International Select℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 2 Class | $82 | 0.74% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 2 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials, information technology, consumer discretionary, materials and consumer staples sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the communication services and financials sectors and smaller allocations to the health care and consumer discretionary sectors buoyed the Fund relative performance during the annual period.

**Individual holdings** \| Positions in Bank of Ireland, an Irish diversified financial services company; Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Standard Chartered, a London-based provider of banking and financial services; and BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, health care and communication services sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the consumer staples and real estate sectors and a small allocation to the industrials sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in adidas, a German manufacturer of athletic and lifestyle products; OMRON Corporation, a Japanese maker of automation components, equipment, and system IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Rolls-Royce Holdings, a London-based manufacturer of integrated power systems for use in the air, on land, and at sea, and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International Select℠ \| Institutional 2 Class **\|** ASR112_15_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 2 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g24c25.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International Select℠ Institutional 2 Class ($19312)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE Growth Index (Net) ($20466)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9498 | $9277 | $9364 |
| **02/16** | $9309 | $9107 | $9201 |
| **03/16** | $9811 | $9699 | $9793 |
| **04/16** | $9857 | $9980 | $9979 |
| **05/16** | $9926 | $9890 | $9954 |
| **06/16** | $9830 | $9558 | $9778 |
| **07/16** | $10285 | $10042 | $10256 |
| **08/16** | $10506 | $10049 | $10112 |
| **09/16** | $10893 | $10173 | $10263 |
| **10/16** | $10355 | $9965 | $9821 |
| **11/16** | $9931 | $9766 | $9486 |
| **12/16** | $10125 | $10100 | $9696 |
| **01/17** | $10661 | $10393 | $10022 |
| **02/17** | $10898 | $10542 | $10244 |
| **03/17** | $11247 | $10832 | $10522 |
| **04/17** | $11791 | $11107 | $10838 |
| **05/17** | $12136 | $11515 | $11387 |
| **06/17** | $12187 | $11495 | $11313 |
| **07/17** | $12685 | $11826 | $11587 |
| **08/17** | $12694 | $11822 | $11652 |
| **09/17** | $12861 | $12116 | $11872 |
| **10/17** | $13294 | $12300 | $12142 |
| **11/17** | $13559 | $12429 | $12288 |
| **12/17** | $13742 | $12628 | $12494 |
| **01/18** | $14368 | $13262 | $13073 |
| **02/18** | $13808 | $12663 | $12514 |
| **03/18** | $13817 | $12435 | $12364 |
| **04/18** | $13803 | $12719 | $12550 |
| **05/18** | $13966 | $12433 | $12525 |
| **06/18** | $14013 | $12281 | $12377 |
| **07/18** | $14349 | $12584 | $12633 |
| **08/18** | $14354 | $12341 | $12598 |
| **09/18** | $14340 | $12448 | $12566 |
| **10/18** | $12907 | $11457 | $11409 |
| **11/18** | $12762 | $11442 | $11443 |
| **12/18** | $12071 | $10887 | $10891 |
| **01/19** | $13142 | $11602 | $11593 |
| **02/19** | $13554 | $11898 | $11992 |
| **03/19** | $13962 | $11973 | $12203 |
| **04/19** | $14681 | $12310 | $12602 |
| **05/19** | $13932 | $11719 | $12115 |
| **06/19** | $14899 | $12414 | $12902 |
| **07/19** | $14537 | $12256 | $12855 |
| **08/19** | $14435 | $11939 | $12699 |
| **09/19** | $14451 | $12281 | $12844 |
| **10/19** | $15022 | $12722 | $13304 |
| **11/19** | $15516 | $12866 | $13543 |
| **12/19** | $16154 | $13284 | $13930 |
| **01/20** | $15872 | $13006 | $13850 |
| **02/20** | $14701 | $11831 | $12654 |
| **03/20** | $12021 | $10252 | $11490 |
| **04/20** | $13358 | $10914 | $12342 |
| **05/20** | $14723 | $11389 | $13016 |
| **06/20** | $15166 | $11777 | $13438 |
| **07/20** | $16125 | $12051 | $14041 |
| **08/20** | $16917 | $12671 | $14666 |
| **09/20** | $16906 | $12342 | $14570 |
| **10/20** | $16413 | $11849 | $13993 |
| **11/20** | $17987 | $13686 | $15712 |
| **12/20** | $19162 | $14322 | $16478 |
| **01/21** | $18813 | $14169 | $16254 |
| **02/21** | $18464 | $14487 | $16198 |
| **03/21** | $18425 | $14820 | $16385 |
| **04/21** | $19922 | $15266 | $17075 |
| **05/21** | $20066 | $15764 | $17592 |
| **06/21** | $20020 | $15587 | $17600 |
| **07/21** | $20679 | $15704 | $17903 |
| **08/21** | $21382 | $15981 | $18325 |
| **09/21** | $20416 | $15517 | $17612 |
| **10/21** | $21426 | $15899 | $18189 |
| **11/21** | $20701 | $15159 | $17572 |
| **12/21** | $21245 | $15935 | $18332 |
| **01/22** | $18221 | $15165 | $16408 |
| **02/22** | $17678 | $14897 | $16044 |
| **03/22** | $17297 | $14993 | $16143 |
| **04/22** | $15426 | $14023 | $14851 |
| **05/22** | $15409 | $14128 | $14678 |
| **06/22** | $13591 | $12817 | $13418 |
| **07/22** | $15101 | $13456 | $14481 |
| **08/22** | $13760 | $12817 | $13603 |
| **09/22** | $11759 | $11618 | $12278 |
| **10/22** | $12366 | $12242 | $12809 |
| **11/22** | $14100 | $13621 | $14287 |
| **12/22** | $13475 | $13632 | $14126 |
| **01/23** | $14913 | $14736 | $15325 |
| **02/23** | $14482 | $14429 | $14897 |
| **03/23** | $14961 | $14786 | $15693 |
| **04/23** | $15107 | $15204 | $16074 |
| **05/23** | $14925 | $14560 | $15578 |
| **06/23** | $15283 | $15223 | $16128 |
| **07/23** | $15386 | $15715 | $16445 |
| **08/23** | $14700 | $15113 | $15673 |
| **09/23** | $13585 | $14597 | $14734 |
| **10/23** | $12924 | $14005 | $14190 |
| **11/23** | $14937 | $15305 | $15710 |
| **12/23** | $15974 | $16118 | $16609 |
| **01/24** | $15446 | $16211 | $16806 |
| **02/24** | $15907 | $16508 | $17373 |
| **03/24** | $16520 | $17051 | $17777 |
| **04/24** | $15932 | $16614 | $17071 |
| **05/24** | $16847 | $17258 | $17722 |
| **06/24** | $16665 | $16979 | $17643 |
| **07/24** | $16965 | $17477 | $17860 |
| **08/24** | $17505 | $18046 | $18564 |
| **09/24** | $17548 | $18212 | $18645 |
| **10/24** | $16340 | $17222 | $17494 |
| **11/24** | $16683 | $17124 | $17430 |
| **12/24** | $15996 | $16735 | $16948 |
| **01/25** | $16787 | $17614 | $17865 |
| **02/25** | $16959 | $17956 | $17888 |
| **03/25** | $16315 | $17883 | $17310 |
| **04/25** | $17070 | $18702 | $18202 |
| **05/25** | $17689 | $19558 | $19144 |
| **06/25** | $18343 | $19989 | $19653 |
| **07/25** | $17737 | $19708 | $19062 |
| **08/25** | $18198 | $20549 | $19597 |
| **09/25** | $18975 | $20942 | $20092 |
| **10/25** | $19114 | $21188 | $20413 |
| **11/25** | $18893 | $21320 | $20112 |
| **12/25** | $19312 | $21959 | $20466 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 2 Class<sup>Footnote Reference(a)</sup> | 20.73 | 0.16 | 6.80 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE Growth Index (Net) | 20.76 | 4.43 | 7.42 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $199839273 |
| **Total number of portfolio holdings** | 61 |
| **Management services fees (represents 0.87% of Fund average net assets)** | $1715600 |
| **Portfolio turnover for the reporting period** | 21% |

---

Columbia Acorn International Select℠ \| Institutional 2 Class **\|** ASR112_15_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 27.9% |
| United Kingdom | 21.6% |
| France | 18.1% |
| Germany | 7.6% |
| Switzerland | 5.7% |
| Netherlands | 3.6% |
| United States | 3.5% |
| Spain | 2.8% |
| Ireland | 2.6% |
| Italy | 1.8% |
| Other | 5.2% |

---

### Top Holdings

---

| | |
|:---|:---|
| Schneider Electric SE | 4.1% |
| ASML Holding NV | 3.6% |
| Taisei Corp. | 3.1% |
| LVMH Moet Hennessy Louis Vuitton SE | 3.1% |
| Airbus Group SE | 3.0% |
| 3i Group PLC | 2.9% |
| Industria de Diseno Textil SA | 2.8% |
| Standard Chartered PLC | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Capcom Co., Ltd. | 2.5% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.9% |
| Information Technology | 16.7% |
| Financials | 14.4% |
| Communication Services | 10.6% |
| Consumer Discretionary | 10.2% |
| Health Care | 8.2% |
| Consumer Staples | 6.2% |
| Materials | 3.2% |
| Real Estate | 1.0% |
| Energy | 0.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International Select℠ \| Institutional 2 Class **\|** ASR112_15_(02/26) \|

# Columbia Acorn International Select℠
Institutional 3 Class \| CSIRX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International Select℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 3 Class | $76 | 0.69% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 3 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials, information technology, consumer discretionary, materials and consumer staples sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the communication services and financials sectors and smaller allocations to the health care and consumer discretionary sectors buoyed the Fund relative performance during the annual period.

**Individual holdings** \| Positions in Bank of Ireland, an Irish diversified financial services company; Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Standard Chartered, a London-based provider of banking and financial services; and BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, health care and communication services sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the consumer staples and real estate sectors and a small allocation to the industrials sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in adidas, a German manufacturer of athletic and lifestyle products; OMRON Corporation, a Japanese maker of automation components, equipment, and system IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Rolls-Royce Holdings, a London-based manufacturer of integrated power systems for use in the air, on land, and at sea, and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International Select℠ \| Institutional 3 Class **\|** ASR112_17_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 3 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g91s03.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International Select℠ Institutional 3 Class ($19401)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE Growth Index (Net) ($20466)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9498 | $9277 | $9364 |
| **02/16** | $9304 | $9107 | $9201 |
| **03/16** | $9811 | $9699 | $9793 |
| **04/16** | $9857 | $9980 | $9979 |
| **05/16** | $9926 | $9890 | $9954 |
| **06/16** | $9830 | $9558 | $9778 |
| **07/16** | $10286 | $10042 | $10256 |
| **08/16** | $10511 | $10049 | $10112 |
| **09/16** | $10894 | $10173 | $10263 |
| **10/16** | $10355 | $9965 | $9821 |
| **11/16** | $9936 | $9766 | $9486 |
| **12/16** | $10129 | $10100 | $9696 |
| **01/17** | $10665 | $10393 | $10022 |
| **02/17** | $10902 | $10542 | $10244 |
| **03/17** | $11256 | $10832 | $10522 |
| **04/17** | $11797 | $11107 | $10838 |
| **05/17** | $12142 | $11515 | $11387 |
| **06/17** | $12193 | $11495 | $11313 |
| **07/17** | $12691 | $11826 | $11587 |
| **08/17** | $12701 | $11822 | $11652 |
| **09/17** | $12873 | $12116 | $11872 |
| **10/17** | $13306 | $12300 | $12142 |
| **11/17** | $13572 | $12429 | $12288 |
| **12/17** | $13756 | $12628 | $12494 |
| **01/18** | $14378 | $13262 | $13073 |
| **02/18** | $13822 | $12663 | $12514 |
| **03/18** | $13831 | $12435 | $12364 |
| **04/18** | $13817 | $12719 | $12550 |
| **05/18** | $13981 | $12433 | $12525 |
| **06/18** | $14028 | $12281 | $12377 |
| **07/18** | $14364 | $12584 | $12633 |
| **08/18** | $14374 | $12341 | $12598 |
| **09/18** | $14360 | $12448 | $12566 |
| **10/18** | $12924 | $11457 | $11409 |
| **11/18** | $12779 | $11442 | $11443 |
| **12/18** | $12087 | $10887 | $10891 |
| **01/19** | $13165 | $11602 | $11593 |
| **02/19** | $13573 | $11898 | $11992 |
| **03/19** | $13986 | $11973 | $12203 |
| **04/19** | $14701 | $12310 | $12602 |
| **05/19** | $13955 | $11719 | $12115 |
| **06/19** | $14926 | $12414 | $12902 |
| **07/19** | $14563 | $12256 | $12855 |
| **08/19** | $14461 | $11939 | $12699 |
| **09/19** | $14476 | $12281 | $12844 |
| **10/19** | $15054 | $12722 | $13304 |
| **11/19** | $15544 | $12866 | $13543 |
| **12/19** | $16185 | $13284 | $13930 |
| **01/20** | $15902 | $13006 | $13850 |
| **02/20** | $14728 | $11831 | $12654 |
| **03/20** | $12042 | $10252 | $11490 |
| **04/20** | $13388 | $10914 | $12342 |
| **05/20** | $14756 | $11389 | $13016 |
| **06/20** | $15194 | $11777 | $13438 |
| **07/20** | $16156 | $12051 | $14041 |
| **08/20** | $16951 | $12671 | $14666 |
| **09/20** | $16940 | $12342 | $14570 |
| **10/20** | $16445 | $11849 | $13993 |
| **11/20** | $18023 | $13686 | $15712 |
| **12/20** | $19207 | $14322 | $16478 |
| **01/21** | $18857 | $14169 | $16254 |
| **02/21** | $18507 | $14487 | $16198 |
| **03/21** | $18468 | $14820 | $16385 |
| **04/21** | $19968 | $15266 | $17075 |
| **05/21** | $20113 | $15764 | $17592 |
| **06/21** | $20068 | $15587 | $17600 |
| **07/21** | $20728 | $15704 | $17903 |
| **08/21** | $21433 | $15981 | $18325 |
| **09/21** | $20471 | $15517 | $17612 |
| **10/21** | $21483 | $15899 | $18189 |
| **11/21** | $20756 | $15159 | $17572 |
| **12/21** | $21306 | $15935 | $18332 |
| **01/22** | $18273 | $15165 | $16408 |
| **02/22** | $17721 | $14897 | $16044 |
| **03/22** | $17346 | $14993 | $16143 |
| **04/22** | $15468 | $14023 | $14851 |
| **05/22** | $15450 | $14128 | $14678 |
| **06/22** | $13632 | $12817 | $13418 |
| **07/22** | $15147 | $13456 | $14481 |
| **08/22** | $13796 | $12817 | $13603 |
| **09/22** | $11794 | $11618 | $12278 |
| **10/22** | $12403 | $12242 | $12809 |
| **11/22** | $14143 | $13621 | $14287 |
| **12/22** | $13516 | $13632 | $14126 |
| **01/23** | $14965 | $14736 | $15325 |
| **02/23** | $14533 | $14429 | $14897 |
| **03/23** | $15007 | $14786 | $15693 |
| **04/23** | $15160 | $15204 | $16074 |
| **05/23** | $14971 | $14560 | $15578 |
| **06/23** | $15336 | $15223 | $16128 |
| **07/23** | $15439 | $15715 | $16445 |
| **08/23** | $14752 | $15113 | $15673 |
| **09/23** | $13632 | $14597 | $14734 |
| **10/23** | $12969 | $14005 | $14190 |
| **11/23** | $14989 | $15305 | $15710 |
| **12/23** | $16036 | $16118 | $16609 |
| **01/24** | $15506 | $16211 | $16806 |
| **02/24** | $15969 | $16508 | $17373 |
| **03/24** | $16584 | $17051 | $17777 |
| **04/24** | $15993 | $16614 | $17071 |
| **05/24** | $16912 | $17258 | $17722 |
| **06/24** | $16730 | $16979 | $17643 |
| **07/24** | $17032 | $17477 | $17860 |
| **08/24** | $17574 | $18046 | $18564 |
| **09/24** | $17617 | $18212 | $18645 |
| **10/24** | $16404 | $17222 | $17494 |
| **11/24** | $16755 | $17124 | $17430 |
| **12/24** | $16059 | $16735 | $16948 |
| **01/25** | $16859 | $17614 | $17865 |
| **02/25** | $17026 | $17956 | $17888 |
| **03/25** | $16385 | $17883 | $17310 |
| **04/25** | $17143 | $18702 | $18202 |
| **05/25** | $17765 | $19558 | $19144 |
| **06/25** | $18423 | $19989 | $19653 |
| **07/25** | $17814 | $19708 | $19062 |
| **08/25** | $18284 | $20549 | $19597 |
| **09/25** | $19064 | $20942 | $20092 |
| **10/25** | $19197 | $21188 | $20413 |
| **11/25** | $18981 | $21320 | $20112 |
| **12/25** | $19401 | $21959 | $20466 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 3 Class<sup>Footnote Reference(a)</sup> | 20.81 | 0.20 | 6.85 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE Growth Index (Net) | 20.76 | 4.43 | 7.42 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $199839273 |
| **Total number of portfolio holdings** | 61 |
| **Management services fees (represents 0.87% of Fund average net assets)** | $1715600 |
| **Portfolio turnover for the reporting period** | 21% |

---

Columbia Acorn International Select℠ \| Institutional 3 Class **\|** ASR112_17_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 27.9% |
| United Kingdom | 21.6% |
| France | 18.1% |
| Germany | 7.6% |
| Switzerland | 5.7% |
| Netherlands | 3.6% |
| United States | 3.5% |
| Spain | 2.8% |
| Ireland | 2.6% |
| Italy | 1.8% |
| Other | 5.2% |

---

### Top Holdings

---

| | |
|:---|:---|
| Schneider Electric SE | 4.1% |
| ASML Holding NV | 3.6% |
| Taisei Corp. | 3.1% |
| LVMH Moet Hennessy Louis Vuitton SE | 3.1% |
| Airbus Group SE | 3.0% |
| 3i Group PLC | 2.9% |
| Industria de Diseno Textil SA | 2.8% |
| Standard Chartered PLC | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Capcom Co., Ltd. | 2.5% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.9% |
| Information Technology | 16.7% |
| Financials | 14.4% |
| Communication Services | 10.6% |
| Consumer Discretionary | 10.2% |
| Health Care | 8.2% |
| Consumer Staples | 6.2% |
| Materials | 3.2% |
| Real Estate | 1.0% |
| Energy | 0.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International Select℠ \| Institutional 3 Class **\|** ASR112_17_(02/26) \|

# Columbia Acorn International Select℠
Institutional Class \| ACFFX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Acorn International Select℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional Class | $96 | 0.87% |

---

## Management's Discussion of Fund Performance
The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Stock selection** \| Selections in the financials, information technology, consumer discretionary, materials and consumer staples sectors boosted the Fund's relative performance most during the annual period.

**Allocations** \| Larger allocations to the communication services and financials sectors and smaller allocations to the health care and consumer discretionary sectors buoyed the Fund relative performance during the annual period.

**Individual holdings** \| Positions in Bank of Ireland, an Irish diversified financial services company; Taisei Corporation, a Japanese construction and engineering company; Kokusai Electric Corporation, a Japanese manufacturer of electrical equipment, semiconductor systems and industrial video cameras; Standard Chartered, a London-based provider of banking and financial services; and BELIMO Holding, a Swiss heating, ventilation and air conditioning manufacturer, were among the top contributors to the Fund's relative performance.

### Top Performance Detractors
**Stock selection** \| Selections in the industrials, health care and communication services sectors hurt the Fund's relative performance during the annual period.

**Allocations** \| Large weightings in the consumer staples and real estate sectors and a small allocation to the industrials sector detracted from the Fund's relative performance.

**Individual holdings** \| Fund positions in adidas, a German manufacturer of athletic and lifestyle products; OMRON Corporation, a Japanese maker of automation components, equipment, and system IMCD N.V., a distributor of specialty chemicals and ingredients headquartered in the Netherlands; Rolls-Royce Holdings, a London-based manufacturer of integrated power systems for use in the air, on land, and at sea, and Recruit Holdings, a Japanese provider of human resources technology, were top detractors from the Fund's relative performance during the period.

Columbia Acorn International Select℠ \| Institutional Class **\|** ASR112_08_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g12y26.jpg)

---

| | | | |
|:---|:---|:---|:---|
| | **Columbia Acorn International Select℠ Institutional Class ($19125)** | **MSCI EAFE Index (Net) ($21959)** | **MSCI EAFE Growth Index (Net) ($20466)** |
| **12/15** | $10000 | $10000 | $10000 |
| **01/16** | $9504 | $9277 | $9364 |
| **02/16** | $9310 | $9107 | $9201 |
| **03/16** | $9810 | $9699 | $9793 |
| **04/16** | $9856 | $9980 | $9979 |
| **05/16** | $9926 | $9890 | $9954 |
| **06/16** | $9829 | $9558 | $9778 |
| **07/16** | $10283 | $10042 | $10256 |
| **08/16** | $10505 | $10049 | $10112 |
| **09/16** | $10890 | $10173 | $10263 |
| **10/16** | $10352 | $9965 | $9821 |
| **11/16** | $9926 | $9766 | $9486 |
| **12/16** | $10118 | $10100 | $9696 |
| **01/17** | $10657 | $10393 | $10022 |
| **02/17** | $10891 | $10542 | $10244 |
| **03/17** | $11242 | $10832 | $10522 |
| **04/17** | $11781 | $11107 | $10838 |
| **05/17** | $12127 | $11515 | $11387 |
| **06/17** | $12174 | $11495 | $11313 |
| **07/17** | $12675 | $11826 | $11587 |
| **08/17** | $12680 | $11822 | $11652 |
| **09/17** | $12848 | $12116 | $11872 |
| **10/17** | $13284 | $12300 | $12142 |
| **11/17** | $13546 | $12429 | $12288 |
| **12/17** | $13731 | $12628 | $12494 |
| **01/18** | $14351 | $13262 | $13073 |
| **02/18** | $13792 | $12663 | $12514 |
| **03/18** | $13801 | $12435 | $12364 |
| **04/18** | $13783 | $12719 | $12550 |
| **05/18** | $13942 | $12433 | $12525 |
| **06/18** | $13989 | $12281 | $12377 |
| **07/18** | $14327 | $12584 | $12633 |
| **08/18** | $14332 | $12341 | $12598 |
| **09/18** | $14313 | $12448 | $12566 |
| **10/18** | $12881 | $11457 | $11409 |
| **11/18** | $12740 | $11442 | $11443 |
| **12/18** | $12045 | $10887 | $10891 |
| **01/19** | $13118 | $11602 | $11593 |
| **02/19** | $13523 | $11898 | $11992 |
| **03/19** | $13932 | $11973 | $12203 |
| **04/19** | $14646 | $12310 | $12602 |
| **05/19** | $13897 | $11719 | $12115 |
| **06/19** | $14862 | $12414 | $12902 |
| **07/19** | $14503 | $12256 | $12855 |
| **08/19** | $14401 | $11939 | $12699 |
| **09/19** | $14411 | $12281 | $12844 |
| **10/19** | $14985 | $12722 | $13304 |
| **11/19** | $15472 | $12866 | $13543 |
| **12/19** | $16105 | $13284 | $13930 |
| **01/20** | $15828 | $13006 | $13850 |
| **02/20** | $14656 | $11831 | $12654 |
| **03/20** | $11979 | $10252 | $11490 |
| **04/20** | $13317 | $10914 | $12342 |
| **05/20** | $14672 | $11389 | $13016 |
| **06/20** | $15112 | $11777 | $13438 |
| **07/20** | $16065 | $12051 | $14041 |
| **08/20** | $16856 | $12671 | $14666 |
| **09/20** | $16840 | $12342 | $14570 |
| **10/20** | $16349 | $11849 | $13993 |
| **11/20** | $17915 | $13686 | $15712 |
| **12/20** | $19085 | $14322 | $16478 |
| **01/21** | $18734 | $14169 | $16254 |
| **02/21** | $18389 | $14487 | $16198 |
| **03/21** | $18350 | $14820 | $16385 |
| **04/21** | $19832 | $15266 | $17075 |
| **05/21** | $19977 | $15764 | $17592 |
| **06/21** | $19928 | $15587 | $17600 |
| **07/21** | $20584 | $15704 | $17903 |
| **08/21** | $21279 | $15981 | $18325 |
| **09/21** | $20326 | $15517 | $17612 |
| **10/21** | $21330 | $15899 | $18189 |
| **11/21** | $20601 | $15159 | $17572 |
| **12/21** | $21145 | $15935 | $18332 |
| **01/22** | $18133 | $15165 | $16408 |
| **02/22** | $17587 | $14897 | $16044 |
| **03/22** | $17205 | $14993 | $16143 |
| **04/22** | $15344 | $14023 | $14851 |
| **05/22** | $15326 | $14128 | $14678 |
| **06/22** | $13518 | $12817 | $13418 |
| **07/22** | $15023 | $13456 | $14481 |
| **08/22** | $13683 | $12817 | $13603 |
| **09/22** | $11697 | $11618 | $12278 |
| **10/22** | $12294 | $12242 | $12809 |
| **11/22** | $14018 | $13621 | $14287 |
| **12/22** | $13396 | $13632 | $14126 |
| **01/23** | $14828 | $14736 | $15325 |
| **02/23** | $14395 | $14429 | $14897 |
| **03/23** | $14871 | $14786 | $15693 |
| **04/23** | $15017 | $15204 | $16074 |
| **05/23** | $14828 | $14560 | $15578 |
| **06/23** | $15187 | $15223 | $16128 |
| **07/23** | $15285 | $15715 | $16445 |
| **08/23** | $14602 | $15113 | $15673 |
| **09/23** | $13494 | $14597 | $14734 |
| **10/23** | $12836 | $14005 | $14190 |
| **11/23** | $14834 | $15305 | $15710 |
| **12/23** | $15864 | $16118 | $16609 |
| **01/24** | $15334 | $16211 | $16806 |
| **02/24** | $15796 | $16508 | $17373 |
| **03/24** | $16400 | $17051 | $17777 |
| **04/24** | $15809 | $16614 | $17071 |
| **05/24** | $16716 | $17258 | $17722 |
| **06/24** | $16534 | $16979 | $17643 |
| **07/24** | $16830 | $17477 | $17860 |
| **08/24** | $17366 | $18046 | $18564 |
| **09/24** | $17409 | $18212 | $18645 |
| **10/24** | $16202 | $17222 | $17494 |
| **11/24** | $16547 | $17124 | $17430 |
| **12/24** | $15857 | $16735 | $16948 |
| **01/25** | $16645 | $17614 | $17865 |
| **02/25** | $16811 | $17956 | $17888 |
| **03/25** | $16171 | $17883 | $17310 |
| **04/25** | $16916 | $18702 | $18202 |
| **05/25** | $17532 | $19558 | $19144 |
| **06/25** | $18177 | $19989 | $19653 |
| **07/25** | $17575 | $19708 | $19062 |
| **08/25** | $18031 | $20549 | $19597 |
| **09/25** | $18798 | $20942 | $20092 |
| **10/25** | $18931 | $21188 | $20413 |
| **11/25** | $18709 | $21320 | $20112 |
| **12/25** | $19125 | $21959 | $20466 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional Class<sup>Footnote Reference(a)</sup> | 20.61 | 0.04 | 6.70 |
| MSCI EAFE Index (Net) | 31.22 | 8.92 | 8.18 |
| MSCI EAFE Growth Index (Net) | 20.76 | 4.43 | 7.42 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to September 3, 2024 reflects returns achieved pursuant to different principal investment strategies. If the Fund's current strategies had been in place for the prior periods, results shown would have been different. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $199839273 |
| **Total number of portfolio holdings** | 61 |
| **Management services fees (represents 0.87% of Fund average net assets)** | $1715600 |
| **Portfolio turnover for the reporting period** | 21% |

---

Columbia Acorn International Select℠ \| Institutional Class **\|** ASR112_08_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

#### Geographic Allocation

---

| | |
|:---|:---|
| Japan | 27.9% |
| United Kingdom | 21.6% |
| France | 18.1% |
| Germany | 7.6% |
| Switzerland | 5.7% |
| Netherlands | 3.6% |
| United States | 3.5% |
| Spain | 2.8% |
| Ireland | 2.6% |
| Italy | 1.8% |
| Other | 5.2% |

---

### Top Holdings

---

| | |
|:---|:---|
| Schneider Electric SE | 4.1% |
| ASML Holding NV | 3.6% |
| Taisei Corp. | 3.1% |
| LVMH Moet Hennessy Louis Vuitton SE | 3.1% |
| Airbus Group SE | 3.0% |
| 3i Group PLC | 2.9% |
| Industria de Diseno Textil SA | 2.8% |
| Standard Chartered PLC | 2.6% |
| Bank of Ireland Group PLC | 2.6% |
| Capcom Co., Ltd. | 2.5% |

---

#### Equity Sector Allocation

---

| | |
|:---|:---|
| Industrials | 27.9% |
| Information Technology | 16.7% |
| Financials | 14.4% |
| Communication Services | 10.6% |
| Consumer Discretionary | 10.2% |
| Health Care | 8.2% |
| Consumer Staples | 6.2% |
| Materials | 3.2% |
| Real Estate | 1.0% |
| Energy | 0.7% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer. Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Fund.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Acorn International Select℠ \| Institutional Class **\|** ASR112_08_(02/26) \|

# Columbia Thermostat Fund℠
Class A \| CTFAX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class A | $53 | 0.49% |

---

## Management's Discussion of Fund Performance
The performance of Class A shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Class A **\|** ASR235_01_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class A shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g27x21.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Class A (including sales charges) ($19509)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $9427 | $10000 | $10000 | $10000 |
| **01/16** | $9289 | $10138 | $9821 | $9504 |
| **02/16** | $9302 | $10210 | $9849 | $9491 |
| **03/16** | $9592 | $10303 | $10228 | $10135 |
| **04/16** | $9677 | $10343 | $10268 | $10174 |
| **05/16** | $9723 | $10345 | $10361 | $10357 |
| **06/16** | $9763 | $10531 | $10468 | $10384 |
| **07/16** | $9884 | $10598 | $10694 | $10766 |
| **08/16** | $9898 | $10586 | $10695 | $10782 |
| **09/16** | $9925 | $10580 | $10693 | $10784 |
| **10/16** | $9851 | $10499 | $10555 | $10587 |
| **11/16** | $9804 | $10250 | $10625 | $10979 |
| **12/16** | $9848 | $10265 | $10738 | $11196 |
| **01/17** | $9895 | $10285 | $10850 | $11408 |
| **02/17** | $9976 | $10354 | $11102 | $11861 |
| **03/17** | $9990 | $10349 | $11105 | $11875 |
| **04/17** | $10057 | $10428 | $11205 | $11997 |
| **05/17** | $10145 | $10509 | $11327 | $12166 |
| **06/17** | $10154 | $10498 | $11357 | $12242 |
| **07/17** | $10223 | $10543 | $11498 | $12494 |
| **08/17** | $10264 | $10638 | $11567 | $12532 |
| **09/17** | $10292 | $10587 | $11659 | $12790 |
| **10/17** | $10326 | $10593 | $11798 | $13089 |
| **11/17** | $10340 | $10580 | $11972 | $13490 |
| **12/17** | $10359 | $10628 | $12066 | $13640 |
| **01/18** | $10366 | $10506 | $12342 | $14421 |
| **02/18** | $10295 | $10406 | $12056 | $13890 |
| **03/18** | $10338 | $10473 | $11941 | $13537 |
| **04/18** | $10288 | $10395 | $11920 | $13589 |
| **05/18** | $10387 | $10469 | $12106 | $13916 |
| **06/18** | $10411 | $10456 | $12136 | $14002 |
| **07/18** | $10468 | $10459 | $12363 | $14523 |
| **08/18** | $10562 | $10526 | $12604 | $14996 |
| **09/18** | $10504 | $10458 | $12599 | $15081 |
| **10/18** | $10318 | $10376 | $12119 | $14050 |
| **11/18** | $10397 | $10438 | $12279 | $14337 |
| **12/18** | $10345 | $10630 | $11837 | $13042 |
| **01/19** | $10704 | $10742 | $12374 | $14087 |
| **02/19** | $10808 | $10736 | $12569 | $14540 |
| **03/19** | $10965 | $10942 | $12812 | $14822 |
| **04/19** | $11025 | $10945 | $13073 | $15422 |
| **05/19** | $10935 | $11139 | $12774 | $14442 |
| **06/19** | $11330 | $11279 | $13304 | $15460 |
| **07/19** | $11405 | $11304 | $13414 | $15682 |
| **08/19** | $11518 | $11597 | $13482 | $15434 |
| **09/19** | $11541 | $11535 | $13572 | $15723 |
| **10/19** | $11654 | $11570 | $13740 | $16063 |
| **11/19** | $11804 | $11564 | $13985 | $16646 |
| **12/19** | $11891 | $11556 | $14192 | $17149 |
| **01/20** | $12033 | $11778 | $14325 | $17142 |
| **02/20** | $12072 | $11990 | $13865 | $15731 |
| **03/20** | $12080 | $11920 | $12968 | $13788 |
| **04/20** | $13126 | $12132 | $13914 | $15555 |
| **05/20** | $13487 | $12188 | $14278 | $16296 |
| **06/20** | $13677 | $12265 | $14465 | $16620 |
| **07/20** | $14139 | $12448 | $14981 | $17558 |
| **08/20** | $14529 | $12348 | $15459 | $18820 |
| **09/20** | $14338 | $12341 | $15161 | $18105 |
| **10/20** | $14171 | $12286 | $14925 | $17623 |
| **11/20** | $15030 | $12406 | $15815 | $19552 |
| **12/20** | $15372 | $12424 | $16130 | $20304 |
| **01/21** | $15313 | $12334 | $15991 | $20099 |
| **02/21** | $15489 | $12156 | $16096 | $20653 |
| **03/21** | $15699 | $12005 | $16348 | $21558 |
| **04/21** | $16119 | $12099 | $16849 | $22708 |
| **05/21** | $16186 | $12139 | $16935 | $22867 |
| **06/21** | $16280 | $12224 | $17192 | $23401 |
| **07/21** | $16416 | $12361 | $17493 | $23956 |
| **08/21** | $16442 | $12337 | $17742 | $24685 |
| **09/21** | $16238 | $12231 | $17253 | $23537 |
| **10/21** | $16289 | $12227 | $17855 | $25186 |
| **11/21** | $16280 | $12263 | $17819 | $25011 |
| **12/21** | $16319 | $12232 | $18196 | $26132 |
| **01/22** | $15944 | $11968 | $17529 | $24780 |
| **02/22** | $15733 | $11835 | $17169 | $24038 |
| **03/22** | $15350 | $11506 | $17249 | $24931 |
| **04/22** | $14736 | $11069 | $16170 | $22757 |
| **05/22** | $14851 | $11141 | $16236 | $22798 |
| **06/22** | $14293 | $10966 | $15439 | $20916 |
| **07/22** | $14864 | $11234 | $16339 | $22845 |
| **08/22** | $14477 | $10917 | $15775 | $21913 |
| **09/22** | $13635 | $10445 | $14708 | $19895 |
| **10/22** | $13848 | $10310 | $15208 | $21506 |
| **11/22** | $14371 | $10689 | $15913 | $22708 |
| **12/22** | $14175 | $10641 | $15419 | $21399 |
| **01/23** | $14767 | $10968 | $16140 | $22744 |
| **02/23** | $14422 | $10684 | $15735 | $22189 |
| **03/23** | $14787 | $10956 | $16223 | $23004 |
| **04/23** | $14866 | $11022 | $16399 | $23363 |
| **05/23** | $14787 | $10902 | $16345 | $23464 |
| **06/23** | $15059 | $10863 | $16856 | $25015 |
| **07/23** | $15168 | $10856 | $17121 | $25818 |
| **08/23** | $15010 | $10786 | $16930 | $25407 |
| **09/23** | $14555 | $10512 | $16311 | $24196 |
| **10/23** | $14248 | $10346 | $16011 | $23687 |
| **11/23** | $15138 | $10815 | $17105 | $25850 |
| **12/23** | $15788 | $11229 | $17821 | $27025 |
| **01/24** | $15799 | $11198 | $17946 | $27479 |
| **02/24** | $15657 | $11040 | $18299 | $28946 |
| **03/24** | $15809 | $11142 | $18677 | $29878 |
| **04/24** | $15364 | $10860 | $18060 | $28657 |
| **05/24** | $15930 | $11044 | $18661 | $30078 |
| **06/24** | $16237 | $11149 | $19084 | $31157 |
| **07/24** | $16593 | $11409 | $19423 | $31537 |
| **08/24** | $17050 | $11573 | $19798 | $32302 |
| **09/24** | $17212 | $11728 | $20142 | $32992 |
| **10/24** | $16847 | $11437 | $19801 | $32692 |
| **11/24** | $17334 | $11558 | $20487 | $34611 |
| **12/24** | $17001 | $11369 | $20075 | $33786 |
| **01/25** | $17220 | $11430 | $20408 | $34727 |
| **02/25** | $17387 | $11681 | $20499 | $34274 |
| **03/25** | $17064 | $11685 | $19926 | $32343 |
| **04/25** | $17335 | $11731 | $19897 | $32124 |
| **05/25** | $17878 | $11647 | $20452 | $34146 |
| **06/25** | $18468 | $11826 | $21129 | $35882 |
| **07/25** | $18625 | $11795 | $21339 | $36687 |
| **08/25** | $18919 | $11936 | $21683 | $37431 |
| **09/25** | $19234 | $12067 | $22196 | $38797 |
| **10/25** | $19433 | $12142 | $22526 | $39706 |
| **11/25** | $19506 | $12217 | $22623 | $39803 |
| **12/25** | $19509 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class A (excluding sales charges)<sup>Footnote Reference(a)</sup> | 14.75 | 4.88 | 7.54 |
| Class A (including sales charges)<sup>Footnote Reference(a)</sup> | 8.18 | 3.64 | 6.91 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Class A **\|** ASR235_01_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Class A **\|** ASR235_01_(02/26) \|

# Columbia Thermostat Fund℠
Class C \| CTFDX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class C | $133 | 1.24% |

---

## Management's Discussion of Fund Performance
The performance of Class C shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Class C **\|** ASR235_04_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class C shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g85z21.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Class C (including sales charges) ($19197)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $10000 | $10000 | $10000 | $10000 |
| **01/16** | $9847 | $10138 | $9821 | $9504 |
| **02/16** | $9861 | $10210 | $9849 | $9491 |
| **03/16** | $10160 | $10303 | $10228 | $10135 |
| **04/16** | $10243 | $10343 | $10268 | $10174 |
| **05/16** | $10285 | $10345 | $10361 | $10357 |
| **06/16** | $10320 | $10531 | $10468 | $10384 |
| **07/16** | $10440 | $10598 | $10694 | $10766 |
| **08/16** | $10454 | $10586 | $10695 | $10782 |
| **09/16** | $10468 | $10580 | $10693 | $10784 |
| **10/16** | $10383 | $10499 | $10555 | $10587 |
| **11/16** | $10334 | $10250 | $10625 | $10979 |
| **12/16** | $10369 | $10265 | $10738 | $11196 |
| **01/17** | $10419 | $10285 | $10850 | $11408 |
| **02/17** | $10490 | $10354 | $11102 | $11861 |
| **03/17** | $10497 | $10349 | $11105 | $11875 |
| **04/17** | $10561 | $10428 | $11205 | $11997 |
| **05/17** | $10646 | $10509 | $11327 | $12166 |
| **06/17** | $10649 | $10498 | $11357 | $12242 |
| **07/17** | $10721 | $10543 | $11498 | $12494 |
| **08/17** | $10757 | $10638 | $11567 | $12532 |
| **09/17** | $10778 | $10587 | $11659 | $12790 |
| **10/17** | $10807 | $10593 | $11798 | $13089 |
| **11/17** | $10814 | $10580 | $11972 | $13490 |
| **12/17** | $10833 | $10628 | $12066 | $13640 |
| **01/18** | $10826 | $10506 | $12342 | $14421 |
| **02/18** | $10745 | $10406 | $12056 | $13890 |
| **03/18** | $10782 | $10473 | $11941 | $13537 |
| **04/18** | $10723 | $10395 | $11920 | $13589 |
| **05/18** | $10826 | $10469 | $12106 | $13916 |
| **06/18** | $10836 | $10456 | $12136 | $14002 |
| **07/18** | $10896 | $10459 | $12363 | $14523 |
| **08/18** | $10985 | $10526 | $12604 | $14996 |
| **09/18** | $10918 | $10458 | $12599 | $15081 |
| **10/18** | $10717 | $10376 | $12119 | $14050 |
| **11/18** | $10791 | $10438 | $12279 | $14337 |
| **12/18** | $10738 | $10630 | $11837 | $13042 |
| **01/19** | $11099 | $10742 | $12374 | $14087 |
| **02/19** | $11192 | $10736 | $12569 | $14540 |
| **03/19** | $11353 | $10942 | $12812 | $14822 |
| **04/19** | $11415 | $10945 | $13073 | $15422 |
| **05/19** | $11315 | $11139 | $12774 | $14442 |
| **06/19** | $11714 | $11279 | $13304 | $15460 |
| **07/19** | $11783 | $11304 | $13414 | $15682 |
| **08/19** | $11884 | $11597 | $13482 | $15434 |
| **09/19** | $11907 | $11535 | $13572 | $15723 |
| **10/19** | $12016 | $11570 | $13740 | $16063 |
| **11/19** | $12163 | $11564 | $13985 | $16646 |
| **12/19** | $12244 | $11556 | $14192 | $17149 |
| **01/20** | $12380 | $11778 | $14325 | $17142 |
| **02/20** | $12421 | $11990 | $13865 | $15731 |
| **03/20** | $12412 | $11920 | $12968 | $13788 |
| **04/20** | $13482 | $12132 | $13914 | $15555 |
| **05/20** | $13843 | $12188 | $14278 | $16296 |
| **06/20** | $14030 | $12265 | $14465 | $16620 |
| **07/20** | $14493 | $12448 | $14981 | $17558 |
| **08/20** | $14884 | $12348 | $15459 | $18820 |
| **09/20** | $14680 | $12341 | $15161 | $18105 |
| **10/20** | $14501 | $12286 | $14925 | $17623 |
| **11/20** | $15371 | $12406 | $15815 | $19552 |
| **12/20** | $15706 | $12424 | $16130 | $20304 |
| **01/21** | $15637 | $12334 | $15991 | $20099 |
| **02/21** | $15816 | $12156 | $16096 | $20653 |
| **03/21** | $16012 | $12005 | $16348 | $21558 |
| **04/21** | $16439 | $12099 | $16849 | $22708 |
| **05/21** | $16490 | $12139 | $16935 | $22867 |
| **06/21** | $16577 | $12224 | $17192 | $23401 |
| **07/21** | $16706 | $12361 | $17493 | $23956 |
| **08/21** | $16723 | $12337 | $17742 | $24685 |
| **09/21** | $16499 | $12231 | $17253 | $23537 |
| **10/21** | $16542 | $12227 | $17855 | $25186 |
| **11/21** | $16525 | $12263 | $17819 | $25011 |
| **12/21** | $16554 | $12232 | $18196 | $26132 |
| **01/22** | $16158 | $11968 | $17529 | $24780 |
| **02/22** | $15935 | $11835 | $17169 | $24038 |
| **03/22** | $15539 | $11506 | $17249 | $24931 |
| **04/22** | $14912 | $11069 | $16170 | $22757 |
| **05/22** | $15018 | $11141 | $16236 | $22798 |
| **06/22** | $14447 | $10966 | $15439 | $20916 |
| **07/22** | $15012 | $11234 | $16339 | $22845 |
| **08/22** | $14613 | $10917 | $15775 | $21913 |
| **09/22** | $13755 | $10445 | $14708 | $19895 |
| **10/22** | $13959 | $10310 | $15208 | $21506 |
| **11/22** | $14476 | $10689 | $15913 | $22708 |
| **12/22** | $14277 | $10641 | $15419 | $21399 |
| **01/23** | $14859 | $10968 | $16140 | $22744 |
| **02/23** | $14504 | $10684 | $15735 | $22189 |
| **03/23** | $14859 | $10956 | $16223 | $23004 |
| **04/23** | $14928 | $11022 | $16399 | $23363 |
| **05/23** | $14849 | $10902 | $16345 | $23464 |
| **06/23** | $15101 | $10863 | $16856 | $25015 |
| **07/23** | $15209 | $10856 | $17121 | $25818 |
| **08/23** | $15032 | $10786 | $16930 | $25407 |
| **09/23** | $14568 | $10512 | $16311 | $24196 |
| **10/23** | $14261 | $10346 | $16011 | $23687 |
| **11/23** | $15140 | $10815 | $17105 | $25850 |
| **12/23** | $15778 | $11229 | $17821 | $27025 |
| **01/24** | $15768 | $11198 | $17946 | $27479 |
| **02/24** | $15618 | $11040 | $18299 | $28946 |
| **03/24** | $15768 | $11142 | $18677 | $29878 |
| **04/24** | $15307 | $10860 | $18060 | $28657 |
| **05/24** | $15868 | $11044 | $18661 | $30078 |
| **06/24** | $16163 | $11149 | $19084 | $31157 |
| **07/24** | $16516 | $11409 | $19423 | $31537 |
| **08/24** | $16949 | $11573 | $19798 | $32302 |
| **09/24** | $17110 | $11728 | $20142 | $32992 |
| **10/24** | $16727 | $11437 | $19801 | $32692 |
| **11/24** | $17201 | $11558 | $20487 | $34611 |
| **12/24** | $16861 | $11369 | $20075 | $33786 |
| **01/25** | $17066 | $11430 | $20408 | $34727 |
| **02/25** | $17220 | $11681 | $20499 | $34274 |
| **03/25** | $16891 | $11685 | $19926 | $32343 |
| **04/25** | $17148 | $11731 | $19897 | $32124 |
| **05/25** | $17683 | $11647 | $20452 | $34146 |
| **06/25** | $18242 | $11826 | $21129 | $35882 |
| **07/25** | $18387 | $11795 | $21339 | $36687 |
| **08/25** | $18666 | $11936 | $21683 | $37431 |
| **09/25** | $18966 | $12067 | $22196 | $38797 |
| **10/25** | $19152 | $12142 | $22526 | $39706 |
| **11/25** | $19213 | $12217 | $22623 | $39803 |
| **12/25** | $19197 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class C (excluding sales charges)<sup>Footnote Reference(a)</sup> | 13.86 | 4.10 | 6.74 |
| Class C (including sales charges)<sup>Footnote Reference(a)</sup> | 12.86 | 4.10 | 6.74 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Class C **\|** ASR235_04_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Class C **\|** ASR235_04_(02/26) \|

# Columbia Thermostat Fund℠
Class S \| COTDX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Class S | $26 | 0.24% |

---

## Management's Discussion of Fund Performance
The performance of Class S shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Class S **\|** ASR235_16_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Class S shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g73a31.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Class S ($21218)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $10000 | $10000 | $10000 | $10000 |
| **01/16** | $9858 | $10138 | $9821 | $9504 |
| **02/16** | $9873 | $10210 | $9849 | $9491 |
| **03/16** | $10184 | $10303 | $10228 | $10135 |
| **04/16** | $10276 | $10343 | $10268 | $10174 |
| **05/16** | $10326 | $10345 | $10361 | $10357 |
| **06/16** | $10369 | $10531 | $10468 | $10384 |
| **07/16** | $10499 | $10598 | $10694 | $10766 |
| **08/16** | $10521 | $10586 | $10695 | $10782 |
| **09/16** | $10550 | $10580 | $10693 | $10784 |
| **10/16** | $10470 | $10499 | $10555 | $10587 |
| **11/16** | $10427 | $10250 | $10625 | $10979 |
| **12/16** | $10472 | $10265 | $10738 | $11196 |
| **01/17** | $10530 | $10285 | $10850 | $11408 |
| **02/17** | $10610 | $10354 | $11102 | $11861 |
| **03/17** | $10632 | $10349 | $11105 | $11875 |
| **04/17** | $10705 | $10428 | $11205 | $11997 |
| **05/17** | $10799 | $10509 | $11327 | $12166 |
| **06/17** | $10809 | $10498 | $11357 | $12242 |
| **07/17** | $10890 | $10543 | $11498 | $12494 |
| **08/17** | $10935 | $10638 | $11567 | $12532 |
| **09/17** | $10965 | $10587 | $11659 | $12790 |
| **10/17** | $11002 | $10593 | $11798 | $13089 |
| **11/17** | $11017 | $10580 | $11972 | $13490 |
| **12/17** | $11050 | $10628 | $12066 | $13640 |
| **01/18** | $11050 | $10506 | $12342 | $14421 |
| **02/18** | $10981 | $10406 | $12056 | $13890 |
| **03/18** | $11027 | $10473 | $11941 | $13537 |
| **04/18** | $10973 | $10395 | $11920 | $13589 |
| **05/18** | $11088 | $10469 | $12106 | $13916 |
| **06/18** | $11114 | $10456 | $12136 | $14002 |
| **07/18** | $11176 | $10459 | $12363 | $14523 |
| **08/18** | $11277 | $10526 | $12604 | $14996 |
| **09/18** | $11223 | $10458 | $12599 | $15081 |
| **10/18** | $11029 | $10376 | $12119 | $14050 |
| **11/18** | $11106 | $10438 | $12279 | $14337 |
| **12/18** | $11063 | $10630 | $11837 | $13042 |
| **01/19** | $11444 | $10742 | $12374 | $14087 |
| **02/19** | $11550 | $10736 | $12569 | $14540 |
| **03/19** | $11728 | $10942 | $12812 | $14822 |
| **04/19** | $11801 | $10945 | $13073 | $15422 |
| **05/19** | $11704 | $11139 | $12774 | $14442 |
| **06/19** | $12124 | $11279 | $13304 | $15460 |
| **07/19** | $12214 | $11304 | $13414 | $15682 |
| **08/19** | $12328 | $11597 | $13482 | $15434 |
| **09/19** | $12361 | $11535 | $13572 | $15723 |
| **10/19** | $12483 | $11570 | $13740 | $16063 |
| **11/19** | $12647 | $11564 | $13985 | $16646 |
| **12/19** | $12739 | $11556 | $14192 | $17149 |
| **01/20** | $12893 | $11778 | $14325 | $17142 |
| **02/20** | $12944 | $11990 | $13865 | $15731 |
| **03/20** | $12953 | $11920 | $12968 | $13788 |
| **04/20** | $14074 | $12132 | $13914 | $15555 |
| **05/20** | $14468 | $12188 | $14278 | $16296 |
| **06/20** | $14675 | $12265 | $14465 | $16620 |
| **07/20** | $15169 | $12448 | $14981 | $17558 |
| **08/20** | $15593 | $12348 | $15459 | $18820 |
| **09/20** | $15394 | $12341 | $15161 | $18105 |
| **10/20** | $15212 | $12286 | $14925 | $17623 |
| **11/20** | $16139 | $12406 | $15815 | $19552 |
| **12/20** | $16514 | $12424 | $16130 | $20304 |
| **01/21** | $16449 | $12334 | $15991 | $20099 |
| **02/21** | $16651 | $12156 | $16096 | $20653 |
| **03/21** | $16871 | $12005 | $16348 | $21558 |
| **04/21** | $17330 | $12099 | $16849 | $22708 |
| **05/21** | $17403 | $12139 | $16935 | $22867 |
| **06/21** | $17515 | $12224 | $17192 | $23401 |
| **07/21** | $17664 | $12361 | $17493 | $23956 |
| **08/21** | $17692 | $12337 | $17742 | $24685 |
| **09/21** | $17469 | $12231 | $17253 | $23537 |
| **10/21** | $17534 | $12227 | $17855 | $25186 |
| **11/21** | $17524 | $12263 | $17819 | $25011 |
| **12/21** | $17573 | $12232 | $18196 | $26132 |
| **01/22** | $17173 | $11968 | $17529 | $24780 |
| **02/22** | $16952 | $11835 | $17169 | $24038 |
| **03/22** | $16541 | $11506 | $17249 | $24931 |
| **04/22** | $15888 | $11069 | $16170 | $22757 |
| **05/22** | $16015 | $11141 | $16236 | $22798 |
| **06/22** | $15413 | $10966 | $15439 | $20916 |
| **07/22** | $16030 | $11234 | $16339 | $22845 |
| **08/22** | $15626 | $10917 | $15775 | $21913 |
| **09/22** | $14711 | $10445 | $14708 | $19895 |
| **10/22** | $14935 | $10310 | $15208 | $21506 |
| **11/22** | $15509 | $10689 | $15913 | $22708 |
| **12/22** | $15302 | $10641 | $15419 | $21399 |
| **01/23** | $15954 | $10968 | $16140 | $22744 |
| **02/23** | $15574 | $10684 | $15735 | $22189 |
| **03/23** | $15976 | $10956 | $16223 | $23004 |
| **04/23** | $16063 | $11022 | $16399 | $23363 |
| **05/23** | $15987 | $10902 | $16345 | $23464 |
| **06/23** | $16275 | $10863 | $16856 | $25015 |
| **07/23** | $16406 | $10856 | $17121 | $25818 |
| **08/23** | $16232 | $10786 | $16930 | $25407 |
| **09/23** | $15742 | $10512 | $16311 | $24196 |
| **10/23** | $15415 | $10346 | $16011 | $23687 |
| **11/23** | $16384 | $10815 | $17105 | $25850 |
| **12/23** | $17086 | $11229 | $17821 | $27025 |
| **01/24** | $17097 | $11198 | $17946 | $27479 |
| **02/24** | $16952 | $11040 | $18299 | $28946 |
| **03/24** | $17120 | $11142 | $18677 | $29878 |
| **04/24** | $16639 | $10860 | $18060 | $28657 |
| **05/24** | $17254 | $11044 | $18661 | $30078 |
| **06/24** | $17593 | $11149 | $19084 | $31157 |
| **07/24** | $17985 | $11409 | $19423 | $31537 |
| **08/24** | $18479 | $11573 | $19798 | $32302 |
| **09/24** | $18669 | $11728 | $20142 | $32992 |
| **10/24** | $18277 | $11437 | $19801 | $32692 |
| **11/24** | $18804 | $11558 | $20487 | $34611 |
| **12/24** | $18448 | $11369 | $20075 | $33786 |
| **01/25** | $18691 | $11430 | $20408 | $34727 |
| **02/25** | $18864 | $11681 | $20499 | $34274 |
| **03/25** | $18529 | $11685 | $19926 | $32343 |
| **04/25** | $18829 | $11731 | $19897 | $32124 |
| **05/25** | $19419 | $11647 | $20452 | $34146 |
| **06/25** | $20060 | $11826 | $21129 | $35882 |
| **07/25** | $20235 | $11795 | $21339 | $36687 |
| **08/25** | $20560 | $11936 | $21683 | $37431 |
| **09/25** | $20909 | $12067 | $22196 | $38797 |
| **10/25** | $21130 | $12142 | $22526 | $39706 |
| **11/25** | $21211 | $12217 | $22623 | $39803 |
| **12/25** | $21218 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Class S<sup>Footnote Reference(a)</sup><sup>Footnote Reference(b)</sup> | 15.02 | 5.14 | 7.81 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The returns shown for periods prior to October 2, 2024 (including returns for the Life of the Fund, if shown, which are since Fund inception) include the returns of Institutional Class. These returns are adjusted to reflect any higher class-related operating expenses of the newer share classes, as applicable. |
| &nbsp;&nbsp;Footnote<sup>(b)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Class S **\|** ASR235_16_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Class S **\|** ASR235_16_(02/26) \|

# Columbia Thermostat Fund℠
Institutional 2 Class \| CQTRX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 2 Class | $22 | 0.20% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 2 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Institutional 2 Class **\|** ASR235_15_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 2 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g53d15.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Institutional 2 Class ($21308)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $10000 | $10000 | $10000 | $10000 |
| **01/16** | $9859 | $10138 | $9821 | $9504 |
| **02/16** | $9873 | $10210 | $9849 | $9491 |
| **03/16** | $10190 | $10303 | $10228 | $10135 |
| **04/16** | $10282 | $10343 | $10268 | $10174 |
| **05/16** | $10331 | $10345 | $10361 | $10357 |
| **06/16** | $10374 | $10531 | $10468 | $10384 |
| **07/16** | $10503 | $10598 | $10694 | $10766 |
| **08/16** | $10525 | $10586 | $10695 | $10782 |
| **09/16** | $10554 | $10580 | $10693 | $10784 |
| **10/16** | $10474 | $10499 | $10555 | $10587 |
| **11/16** | $10431 | $10250 | $10625 | $10979 |
| **12/16** | $10477 | $10265 | $10738 | $11196 |
| **01/17** | $10535 | $10285 | $10850 | $11408 |
| **02/17** | $10615 | $10354 | $11102 | $11861 |
| **03/17** | $10636 | $10349 | $11105 | $11875 |
| **04/17** | $10709 | $10428 | $11205 | $11997 |
| **05/17** | $10803 | $10509 | $11327 | $12166 |
| **06/17** | $10812 | $10498 | $11357 | $12242 |
| **07/17** | $10894 | $10543 | $11498 | $12494 |
| **08/17** | $10938 | $10638 | $11567 | $12532 |
| **09/17** | $10975 | $10587 | $11659 | $12790 |
| **10/17** | $11004 | $10593 | $11798 | $13089 |
| **11/17** | $11026 | $10580 | $11972 | $13490 |
| **12/17** | $11054 | $10628 | $12066 | $13640 |
| **01/18** | $11062 | $10506 | $12342 | $14421 |
| **02/18** | $10986 | $10406 | $12056 | $13890 |
| **03/18** | $11031 | $10473 | $11941 | $13537 |
| **04/18** | $10978 | $10395 | $11920 | $13589 |
| **05/18** | $11100 | $10469 | $12106 | $13916 |
| **06/18** | $11118 | $10456 | $12136 | $14002 |
| **07/18** | $11180 | $10459 | $12363 | $14523 |
| **08/18** | $11288 | $10526 | $12604 | $14996 |
| **09/18** | $11226 | $10458 | $12599 | $15081 |
| **10/18** | $11033 | $10376 | $12119 | $14050 |
| **11/18** | $11118 | $10438 | $12279 | $14337 |
| **12/18** | $11072 | $10630 | $11837 | $13042 |
| **01/19** | $11451 | $10742 | $12374 | $14087 |
| **02/19** | $11564 | $10736 | $12569 | $14540 |
| **03/19** | $11741 | $10942 | $12812 | $14822 |
| **04/19** | $11813 | $10945 | $13073 | $15422 |
| **05/19** | $11717 | $11139 | $12774 | $14442 |
| **06/19** | $12143 | $11279 | $13304 | $15460 |
| **07/19** | $12224 | $11304 | $13414 | $15682 |
| **08/19** | $12346 | $11597 | $13482 | $15434 |
| **09/19** | $12378 | $11535 | $13572 | $15723 |
| **10/19** | $12500 | $11570 | $13740 | $16063 |
| **11/19** | $12662 | $11564 | $13985 | $16646 |
| **12/19** | $12760 | $11556 | $14192 | $17149 |
| **01/20** | $12913 | $11778 | $14325 | $17142 |
| **02/20** | $12965 | $11990 | $13865 | $15731 |
| **03/20** | $12973 | $11920 | $12968 | $13788 |
| **04/20** | $14097 | $12132 | $13914 | $15555 |
| **05/20** | $14488 | $12188 | $14278 | $16296 |
| **06/20** | $14703 | $12265 | $14465 | $16620 |
| **07/20** | $15193 | $12448 | $14981 | $17558 |
| **08/20** | $15624 | $12348 | $15459 | $18820 |
| **09/20** | $15417 | $12341 | $15161 | $18105 |
| **10/20** | $15237 | $12286 | $14925 | $17623 |
| **11/20** | $16167 | $12406 | $15815 | $19552 |
| **12/20** | $16536 | $12424 | $16130 | $20304 |
| **01/21** | $16481 | $12334 | $15991 | $20099 |
| **02/21** | $16682 | $12156 | $16096 | $20653 |
| **03/21** | $16910 | $12005 | $16348 | $21558 |
| **04/21** | $17365 | $12099 | $16849 | $22708 |
| **05/21** | $17438 | $12139 | $16935 | $22867 |
| **06/21** | $17550 | $12224 | $17192 | $23401 |
| **07/21** | $17697 | $12361 | $17493 | $23956 |
| **08/21** | $17725 | $12337 | $17742 | $24685 |
| **09/21** | $17513 | $12231 | $17253 | $23537 |
| **10/21** | $17568 | $12227 | $17855 | $25186 |
| **11/21** | $17568 | $12263 | $17819 | $25011 |
| **12/21** | $17616 | $12232 | $18196 | $26132 |
| **01/22** | $17208 | $11968 | $17529 | $24780 |
| **02/22** | $16988 | $11835 | $17169 | $24038 |
| **03/22** | $16580 | $11506 | $17249 | $24931 |
| **04/22** | $15921 | $11069 | $16170 | $22757 |
| **05/22** | $16047 | $11141 | $16236 | $22798 |
| **06/22** | $15449 | $10966 | $15439 | $20916 |
| **07/22** | $16072 | $11234 | $16339 | $22845 |
| **08/22** | $15660 | $10917 | $15775 | $21913 |
| **09/22** | $14752 | $10445 | $14708 | $19895 |
| **10/22** | $14974 | $10310 | $15208 | $21506 |
| **11/22** | $15555 | $10689 | $15913 | $22708 |
| **12/22** | $15347 | $10641 | $15419 | $21399 |
| **01/23** | $15995 | $10968 | $16140 | $22744 |
| **02/23** | $15617 | $10684 | $15735 | $22189 |
| **03/23** | $16017 | $10956 | $16223 | $23004 |
| **04/23** | $16103 | $11022 | $16399 | $23363 |
| **05/23** | $16027 | $10902 | $16345 | $23464 |
| **06/23** | $16325 | $10863 | $16856 | $25015 |
| **07/23** | $16455 | $10856 | $17121 | $25818 |
| **08/23** | $16282 | $10786 | $16930 | $25407 |
| **09/23** | $15784 | $10512 | $16311 | $24196 |
| **10/23** | $15471 | $10346 | $16011 | $23687 |
| **11/23** | $16433 | $10815 | $17105 | $25850 |
| **12/23** | $17137 | $11229 | $17821 | $27025 |
| **01/24** | $17148 | $11198 | $17946 | $27479 |
| **02/24** | $17004 | $11040 | $18299 | $28946 |
| **03/24** | $17182 | $11142 | $18677 | $29878 |
| **04/24** | $16693 | $10860 | $18060 | $28657 |
| **05/24** | $17315 | $11044 | $18661 | $30078 |
| **06/24** | $17652 | $11149 | $19084 | $31157 |
| **07/24** | $18053 | $11409 | $19423 | $31537 |
| **08/24** | $18544 | $11573 | $19798 | $32302 |
| **09/24** | $18733 | $11728 | $20142 | $32992 |
| **10/24** | $18343 | $11437 | $19801 | $32692 |
| **11/24** | $18867 | $11558 | $20487 | $34611 |
| **12/24** | $18510 | $11369 | $20075 | $33786 |
| **01/25** | $18752 | $11430 | $20408 | $34727 |
| **02/25** | $18936 | $11681 | $20499 | $34274 |
| **03/25** | $18602 | $11685 | $19926 | $32343 |
| **04/25** | $18901 | $11731 | $19897 | $32124 |
| **05/25** | $19499 | $11647 | $20452 | $34146 |
| **06/25** | $20136 | $11826 | $21129 | $35882 |
| **07/25** | $20309 | $11795 | $21339 | $36687 |
| **08/25** | $20644 | $11936 | $21683 | $37431 |
| **09/25** | $20991 | $12067 | $22196 | $38797 |
| **10/25** | $21211 | $12142 | $22526 | $39706 |
| **11/25** | $21303 | $12217 | $22623 | $39803 |
| **12/25** | $21308 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 2 Class<sup>Footnote Reference(a)</sup> | 15.12 | 5.20 | 7.86 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Institutional 2 Class **\|** ASR235_15_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Institutional 2 Class **\|** ASR235_15_(02/26) \|

# Columbia Thermostat Fund℠
Institutional 3 Class \| CYYYX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional 3 Class | $16 | 0.15% |

---

## Management's Discussion of Fund Performance
The performance of Institutional 3 Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Institutional 3 Class **\|** ASR235_17_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional 3 Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g33s93.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Institutional 3 Class ($21399)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $10000 | $10000 | $10000 | $10000 |
| **01/16** | $9859 | $10138 | $9821 | $9504 |
| **02/16** | $9873 | $10210 | $9849 | $9491 |
| **03/16** | $10190 | $10303 | $10228 | $10135 |
| **04/16** | $10282 | $10343 | $10268 | $10174 |
| **05/16** | $10331 | $10345 | $10361 | $10357 |
| **06/16** | $10374 | $10531 | $10468 | $10384 |
| **07/16** | $10504 | $10598 | $10694 | $10766 |
| **08/16** | $10526 | $10586 | $10695 | $10782 |
| **09/16** | $10554 | $10580 | $10693 | $10784 |
| **10/16** | $10475 | $10499 | $10555 | $10587 |
| **11/16** | $10432 | $10250 | $10625 | $10979 |
| **12/16** | $10476 | $10265 | $10738 | $11196 |
| **01/17** | $10534 | $10285 | $10850 | $11408 |
| **02/17** | $10621 | $10354 | $11102 | $11861 |
| **03/17** | $10635 | $10349 | $11105 | $11875 |
| **04/17** | $10715 | $10428 | $11205 | $11997 |
| **05/17** | $10809 | $10509 | $11327 | $12166 |
| **06/17** | $10819 | $10498 | $11357 | $12242 |
| **07/17** | $10900 | $10543 | $11498 | $12494 |
| **08/17** | $10945 | $10638 | $11567 | $12532 |
| **09/17** | $10982 | $10587 | $11659 | $12790 |
| **10/17** | $11019 | $10593 | $11798 | $13089 |
| **11/17** | $11033 | $10580 | $11972 | $13490 |
| **12/17** | $11067 | $10628 | $12066 | $13640 |
| **01/18** | $11067 | $10506 | $12342 | $14421 |
| **02/18** | $10998 | $10406 | $12056 | $13890 |
| **03/18** | $11044 | $10473 | $11941 | $13537 |
| **04/18** | $10991 | $10395 | $11920 | $13589 |
| **05/18** | $11113 | $10469 | $12106 | $13916 |
| **06/18** | $11131 | $10456 | $12136 | $14002 |
| **07/18** | $11200 | $10459 | $12363 | $14523 |
| **08/18** | $11301 | $10526 | $12604 | $14996 |
| **09/18** | $11247 | $10458 | $12599 | $15081 |
| **10/18** | $11053 | $10376 | $12119 | $14050 |
| **11/18** | $11131 | $10438 | $12279 | $14337 |
| **12/18** | $11091 | $10630 | $11837 | $13042 |
| **01/19** | $11470 | $10742 | $12374 | $14087 |
| **02/19** | $11584 | $10736 | $12569 | $14540 |
| **03/19** | $11753 | $10942 | $12812 | $14822 |
| **04/19** | $11826 | $10945 | $13073 | $15422 |
| **05/19** | $11737 | $11139 | $12774 | $14442 |
| **06/19** | $12165 | $11279 | $13304 | $15460 |
| **07/19** | $12246 | $11304 | $13414 | $15682 |
| **08/19** | $12368 | $11597 | $13482 | $15434 |
| **09/19** | $12401 | $11535 | $13572 | $15723 |
| **10/19** | $12523 | $11570 | $13740 | $16063 |
| **11/19** | $12686 | $11564 | $13985 | $16646 |
| **12/19** | $12780 | $11556 | $14192 | $17149 |
| **01/20** | $12943 | $11778 | $14325 | $17142 |
| **02/20** | $12985 | $11990 | $13865 | $15731 |
| **03/20** | $12994 | $11920 | $12968 | $13788 |
| **04/20** | $14130 | $12132 | $13914 | $15555 |
| **05/20** | $14523 | $12188 | $14278 | $16296 |
| **06/20** | $14730 | $12265 | $14465 | $16620 |
| **07/20** | $15231 | $12448 | $14981 | $17558 |
| **08/20** | $15655 | $12348 | $15459 | $18820 |
| **09/20** | $15456 | $12341 | $15161 | $18105 |
| **10/20** | $15274 | $12286 | $14925 | $17623 |
| **11/20** | $16208 | $12406 | $15815 | $19552 |
| **12/20** | $16576 | $12424 | $16130 | $20304 |
| **01/21** | $16521 | $12334 | $15991 | $20099 |
| **02/21** | $16722 | $12156 | $16096 | $20653 |
| **03/21** | $16951 | $12005 | $16348 | $21558 |
| **04/21** | $17408 | $12099 | $16849 | $22708 |
| **05/21** | $17482 | $12139 | $16935 | $22867 |
| **06/21** | $17594 | $12224 | $17192 | $23401 |
| **07/21** | $17742 | $12361 | $17493 | $23956 |
| **08/21** | $17770 | $12337 | $17742 | $24685 |
| **09/21** | $17556 | $12231 | $17253 | $23537 |
| **10/21** | $17612 | $12227 | $17855 | $25186 |
| **11/21** | $17612 | $12263 | $17819 | $25011 |
| **12/21** | $17656 | $12232 | $18196 | $26132 |
| **01/22** | $17257 | $11968 | $17529 | $24780 |
| **02/22** | $17036 | $11835 | $17169 | $24038 |
| **03/22** | $16626 | $11506 | $17249 | $24931 |
| **04/22** | $15964 | $11069 | $16170 | $22757 |
| **05/22** | $16101 | $11141 | $16236 | $22798 |
| **06/22** | $15490 | $10966 | $15439 | $20916 |
| **07/22** | $16116 | $11234 | $16339 | $22845 |
| **08/22** | $15702 | $10917 | $15775 | $21913 |
| **09/22** | $14800 | $10445 | $14708 | $19895 |
| **10/22** | $15023 | $10310 | $15208 | $21506 |
| **11/22** | $15596 | $10689 | $15913 | $22708 |
| **12/22** | $15393 | $10641 | $15419 | $21399 |
| **01/23** | $16045 | $10968 | $16140 | $22744 |
| **02/23** | $15665 | $10684 | $15735 | $22189 |
| **03/23** | $16066 | $10956 | $16223 | $23004 |
| **04/23** | $16153 | $11022 | $16399 | $23363 |
| **05/23** | $16088 | $10902 | $16345 | $23464 |
| **06/23** | $16377 | $10863 | $16856 | $25015 |
| **07/23** | $16507 | $10856 | $17121 | $25818 |
| **08/23** | $16333 | $10786 | $16930 | $25407 |
| **09/23** | $15844 | $10512 | $16311 | $24196 |
| **10/23** | $15518 | $10346 | $16011 | $23687 |
| **11/23** | $16485 | $10815 | $17105 | $25850 |
| **12/23** | $17199 | $11229 | $17821 | $27025 |
| **01/24** | $17211 | $11198 | $17946 | $27479 |
| **02/24** | $17065 | $11040 | $18299 | $28946 |
| **03/24** | $17244 | $11142 | $18677 | $29878 |
| **04/24** | $16753 | $10860 | $18060 | $28657 |
| **05/24** | $17378 | $11044 | $18661 | $30078 |
| **06/24** | $17717 | $11149 | $19084 | $31157 |
| **07/24** | $18121 | $11409 | $19423 | $31537 |
| **08/24** | $18614 | $11573 | $19798 | $32302 |
| **09/24** | $18804 | $11728 | $20142 | $32992 |
| **10/24** | $18412 | $11437 | $19801 | $32692 |
| **11/24** | $18939 | $11558 | $20487 | $34611 |
| **12/24** | $18576 | $11369 | $20075 | $33786 |
| **01/25** | $18830 | $11430 | $20408 | $34727 |
| **02/25** | $19015 | $11681 | $20499 | $34274 |
| **03/25** | $18668 | $11685 | $19926 | $32343 |
| **04/25** | $18969 | $11731 | $19897 | $32124 |
| **05/25** | $19571 | $11647 | $20452 | $34146 |
| **06/25** | $20223 | $11826 | $21129 | $35882 |
| **07/25** | $20398 | $11795 | $21339 | $36687 |
| **08/25** | $20723 | $11936 | $21683 | $37431 |
| **09/25** | $21083 | $12067 | $22196 | $38797 |
| **10/25** | $21304 | $12142 | $22526 | $39706 |
| **11/25** | $21386 | $12217 | $22623 | $39803 |
| **12/25** | $21399 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional 3 Class<sup>Footnote Reference(a)</sup> | 15.20 | 5.24 | 7.90 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Institutional 3 Class **\|** ASR235_17_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Institutional 3 Class **\|** ASR235_17_(02/26) \|

# Columbia Thermostat Fund℠
Institutional Class \| COTZX

![Image](g38195g64o33.jpg)

## Annual Shareholder Report \| December 31, 2025
This annual shareholder report contains important information about Columbia Thermostat Fund℠ (the Fund) for the period of January 1, 2025 to December 31, 2025. You can find additional information about the Fund at columbiathreadneedleus.com/resources/literature. You can also request more information by contacting us at 1-800-345-6611.

#### This report describes changes to the Fund that occurred during the reporting period.

## What were the Fund costs for the reporting period?
(Based on a hypothetical $10,000 investment)

---

| | | |
|:---|:---|:---|
| Class | Cost of a $10,000 investment | Cost paid as a percentage of a $10,000 investment |
| Institutional Class | $26 | 0.24% |

---

## Management's Discussion of Fund Performance
The performance of Institutional Class shares for the period presented is shown in the Average Annual Total Returns table.

### Top Performance Contributors
**Asset allocation effect** \| The Fund began the year underweight in equities, increased exposure to 50% during April's market volatility, and subsequently reduced it to end the year at 30%. This buy low, sell high framework aided performance as the Fund's positioning was the primary driver of performance throughout the year.

**Style effect** \| Style effects in both equity and fixed income contributed to performance over the year. Within equities, our tilt to growth contributed to relative performance, and was enough to offset negative performance from an overweight to small caps. Within fixed income, a tilt towards mortgage-backed securities positively contributed to performance over the year.

**Manager selection effect** \|Manager selection moderately contributed to performance over the year. Fixed income results were positive, primarily due to performance in the Columbia Total Return Bond Fund.

### Top Performance Detractors
**Style effect** \| Within equities, our overweight to small caps detracted from Fund performance. Within fixed income, Treasuries detracted from performance.

**Manager selection effect** \| Performance in the Columbia Research Enhanced Core ETF and Columbia Cornerstone Growth Fund were the largest detractors from relative equity performance.

Columbia Thermostat Fund℠ \| Institutional Class **\|** ASR235_08_(02/26) \|

## Fund Performance
The following shows the change in value of a hypothetical $10,000 investment in Institutional Class shares of the Fund during the stated time period.

### Growth of $10,000
![Growth of 10K Chart](g38195g20c66.jpg)

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Columbia Thermostat Fund℠ Institutional Class ($21218)** | **Bloomberg U.S. Aggregate Bond Index ($12199)** | **50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index ($22613)** | **S&P 500<sup>®</sup> Index ($39827)** |
| **12/15** | $10000 | $10000 | $10000 | $10000 |
| **01/16** | $9858 | $10138 | $9821 | $9504 |
| **02/16** | $9873 | $10210 | $9849 | $9491 |
| **03/16** | $10184 | $10303 | $10228 | $10135 |
| **04/16** | $10276 | $10343 | $10268 | $10174 |
| **05/16** | $10326 | $10345 | $10361 | $10357 |
| **06/16** | $10369 | $10531 | $10468 | $10384 |
| **07/16** | $10499 | $10598 | $10694 | $10766 |
| **08/16** | $10521 | $10586 | $10695 | $10782 |
| **09/16** | $10550 | $10580 | $10693 | $10784 |
| **10/16** | $10470 | $10499 | $10555 | $10587 |
| **11/16** | $10427 | $10250 | $10625 | $10979 |
| **12/16** | $10472 | $10265 | $10738 | $11196 |
| **01/17** | $10530 | $10285 | $10850 | $11408 |
| **02/17** | $10610 | $10354 | $11102 | $11861 |
| **03/17** | $10632 | $10349 | $11105 | $11875 |
| **04/17** | $10705 | $10428 | $11205 | $11997 |
| **05/17** | $10799 | $10509 | $11327 | $12166 |
| **06/17** | $10809 | $10498 | $11357 | $12242 |
| **07/17** | $10890 | $10543 | $11498 | $12494 |
| **08/17** | $10935 | $10638 | $11567 | $12532 |
| **09/17** | $10965 | $10587 | $11659 | $12790 |
| **10/17** | $11002 | $10593 | $11798 | $13089 |
| **11/17** | $11017 | $10580 | $11972 | $13490 |
| **12/17** | $11050 | $10628 | $12066 | $13640 |
| **01/18** | $11050 | $10506 | $12342 | $14421 |
| **02/18** | $10981 | $10406 | $12056 | $13890 |
| **03/18** | $11027 | $10473 | $11941 | $13537 |
| **04/18** | $10973 | $10395 | $11920 | $13589 |
| **05/18** | $11088 | $10469 | $12106 | $13916 |
| **06/18** | $11114 | $10456 | $12136 | $14002 |
| **07/18** | $11176 | $10459 | $12363 | $14523 |
| **08/18** | $11277 | $10526 | $12604 | $14996 |
| **09/18** | $11223 | $10458 | $12599 | $15081 |
| **10/18** | $11029 | $10376 | $12119 | $14050 |
| **11/18** | $11106 | $10438 | $12279 | $14337 |
| **12/18** | $11063 | $10630 | $11837 | $13042 |
| **01/19** | $11444 | $10742 | $12374 | $14087 |
| **02/19** | $11550 | $10736 | $12569 | $14540 |
| **03/19** | $11728 | $10942 | $12812 | $14822 |
| **04/19** | $11801 | $10945 | $13073 | $15422 |
| **05/19** | $11704 | $11139 | $12774 | $14442 |
| **06/19** | $12124 | $11279 | $13304 | $15460 |
| **07/19** | $12214 | $11304 | $13414 | $15682 |
| **08/19** | $12328 | $11597 | $13482 | $15434 |
| **09/19** | $12361 | $11535 | $13572 | $15723 |
| **10/19** | $12483 | $11570 | $13740 | $16063 |
| **11/19** | $12647 | $11564 | $13985 | $16646 |
| **12/19** | $12739 | $11556 | $14192 | $17149 |
| **01/20** | $12893 | $11778 | $14325 | $17142 |
| **02/20** | $12944 | $11990 | $13865 | $15731 |
| **03/20** | $12953 | $11920 | $12968 | $13788 |
| **04/20** | $14074 | $12132 | $13914 | $15555 |
| **05/20** | $14468 | $12188 | $14278 | $16296 |
| **06/20** | $14675 | $12265 | $14465 | $16620 |
| **07/20** | $15169 | $12448 | $14981 | $17558 |
| **08/20** | $15593 | $12348 | $15459 | $18820 |
| **09/20** | $15394 | $12341 | $15161 | $18105 |
| **10/20** | $15212 | $12286 | $14925 | $17623 |
| **11/20** | $16139 | $12406 | $15815 | $19552 |
| **12/20** | $16514 | $12424 | $16130 | $20304 |
| **01/21** | $16449 | $12334 | $15991 | $20099 |
| **02/21** | $16651 | $12156 | $16096 | $20653 |
| **03/21** | $16871 | $12005 | $16348 | $21558 |
| **04/21** | $17330 | $12099 | $16849 | $22708 |
| **05/21** | $17403 | $12139 | $16935 | $22867 |
| **06/21** | $17515 | $12224 | $17192 | $23401 |
| **07/21** | $17664 | $12361 | $17493 | $23956 |
| **08/21** | $17692 | $12337 | $17742 | $24685 |
| **09/21** | $17469 | $12231 | $17253 | $23537 |
| **10/21** | $17534 | $12227 | $17855 | $25186 |
| **11/21** | $17524 | $12263 | $17819 | $25011 |
| **12/21** | $17573 | $12232 | $18196 | $26132 |
| **01/22** | $17173 | $11968 | $17529 | $24780 |
| **02/22** | $16952 | $11835 | $17169 | $24038 |
| **03/22** | $16541 | $11506 | $17249 | $24931 |
| **04/22** | $15888 | $11069 | $16170 | $22757 |
| **05/22** | $16015 | $11141 | $16236 | $22798 |
| **06/22** | $15413 | $10966 | $15439 | $20916 |
| **07/22** | $16030 | $11234 | $16339 | $22845 |
| **08/22** | $15626 | $10917 | $15775 | $21913 |
| **09/22** | $14711 | $10445 | $14708 | $19895 |
| **10/22** | $14935 | $10310 | $15208 | $21506 |
| **11/22** | $15509 | $10689 | $15913 | $22708 |
| **12/22** | $15302 | $10641 | $15419 | $21399 |
| **01/23** | $15954 | $10968 | $16140 | $22744 |
| **02/23** | $15574 | $10684 | $15735 | $22189 |
| **03/23** | $15976 | $10956 | $16223 | $23004 |
| **04/23** | $16063 | $11022 | $16399 | $23363 |
| **05/23** | $15987 | $10902 | $16345 | $23464 |
| **06/23** | $16275 | $10863 | $16856 | $25015 |
| **07/23** | $16406 | $10856 | $17121 | $25818 |
| **08/23** | $16232 | $10786 | $16930 | $25407 |
| **09/23** | $15742 | $10512 | $16311 | $24196 |
| **10/23** | $15415 | $10346 | $16011 | $23687 |
| **11/23** | $16384 | $10815 | $17105 | $25850 |
| **12/23** | $17086 | $11229 | $17821 | $27025 |
| **01/24** | $17097 | $11198 | $17946 | $27479 |
| **02/24** | $16952 | $11040 | $18299 | $28946 |
| **03/24** | $17120 | $11142 | $18677 | $29878 |
| **04/24** | $16639 | $10860 | $18060 | $28657 |
| **05/24** | $17254 | $11044 | $18661 | $30078 |
| **06/24** | $17593 | $11149 | $19084 | $31157 |
| **07/24** | $17985 | $11409 | $19423 | $31537 |
| **08/24** | $18479 | $11573 | $19798 | $32302 |
| **09/24** | $18669 | $11728 | $20142 | $32992 |
| **10/24** | $18277 | $11437 | $19801 | $32692 |
| **11/24** | $18804 | $11558 | $20487 | $34611 |
| **12/24** | $18448 | $11369 | $20075 | $33786 |
| **01/25** | $18691 | $11430 | $20408 | $34727 |
| **02/25** | $18864 | $11681 | $20499 | $34274 |
| **03/25** | $18529 | $11685 | $19926 | $32343 |
| **04/25** | $18829 | $11731 | $19897 | $32124 |
| **05/25** | $19419 | $11647 | $20452 | $34146 |
| **06/25** | $20060 | $11826 | $21129 | $35882 |
| **07/25** | $20235 | $11795 | $21339 | $36687 |
| **08/25** | $20560 | $11936 | $21683 | $37431 |
| **09/25** | $20909 | $12067 | $22196 | $38797 |
| **10/25** | $21130 | $12142 | $22526 | $39706 |
| **11/25** | $21211 | $12217 | $22623 | $39803 |
| **12/25** | $21218 | $12199 | $22613 | $39827 |

---

---

| | | | |
|:---|:---|:---|:---|
| Average Annual Total Returns (%) | 1 year | 5 years | 10 years |
| Institutional Class<sup>Footnote Reference(a)</sup> | 15.02 | 5.14 | 7.81 |
| Bloomberg U.S. Aggregate Bond Index | 7.30 | (0.36) | 2.01 |
| 50% S&P 500<sup>®</sup> Index, 50% Bloomberg U.S. Aggregate Bond Index | 12.64 | 6.99 | 8.50 |
| S&P 500<sup>®</sup> Index | 17.88 | 14.42 | 14.82 |

---

---

| | |
|:---|:---|
| Footnote | Description |
| &nbsp;&nbsp;Footnote<sup>(a)</sup> | &nbsp;&nbsp;The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table. |

---

**The Fund's past performance is not a good predictor of the Fund's future performance.** Performance does not reflect the deduction of taxes that a shareholder may pay on fund distributions or on the redemptions of fund shares. Performance results reflect the effect of any fee waivers/expense reimbursements, if applicable. All results shown assume reinvestment of distributions. Visit columbiathreadneedleus.com/investment-products/mutual-funds for more recent performance information.

## Key Fund Statistics

---

| | |
|:---|:---|
| **Fund net assets** | $1296646599 |
| **Total number of portfolio holdings** | 13 |
| **Management services fees (represents 0.10% of Fund average net assets)** | $1237358 |
| **Portfolio turnover for the reporting period** | 84% |

---

Columbia Thermostat Fund℠ \| Institutional Class **\|** ASR235_08_(02/26) \|

## Graphical Representation of Fund Holdings
The tables below show the investment makeup of the Fund represented as a percentage of Fund net assets. Derivatives are excluded from the tables unless otherwise noted. The Fund's portfolio composition is subject to change.

### Top Holdings

---

| | |
|:---|:---|
| Columbia Total Return Bond Fund, Institutional 3 Class | 17.4% |
| Columbia Select Corporate Income Fund, Institutional 3 Class | 13.9% |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class | 13.8% |
| Columbia Quality Income Fund, Institutional 3 Class | 10.4% |
| Columbia Contrarian Core Fund, Institutional 3 Class | 7.6% |
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class | 7.5% |
| Columbia High Yield Bond Fund, Institutional 3 Class | 7.0% |
| Columbia Diversified Fixed Income Allocation ETF | 6.9% |
| Columbia Large Cap Index Fund, Institutional 3 Class | 6.0% |
| Columbia Research Enhanced Core ETF | 6.0% |

---

#### Asset Categories

---

| | |
|:---|:---|
| Fixed Income Funds | 62.5% |
| Equity Funds | 24.1% |
| Exchange-Traded Fixed Income Funds | 6.9% |
| Exchange-Traded Equity Funds | 6.0% |
| Other | 0.5% |

---

## Certain Fund Changes
This is a summary of the changes to the Fund. For more complete information, you may review the Fund's prospectus, which is available at columbiathreadneedleus.com/resources/literature or upon request at 1-800-345-6611.

On June 26, 2025, the Fund's Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Fund's Management Agreement with Columbia Wanger Asset Management, LLC (CWAM) were transferred to its parent company Columbia Management Investment Advisers, LLC on July 7, 2025. The services provided to, and management fees paid by, the Fund were not changed as a result of that transfer.

## Availability of Additional Information
For additional information about the Fund, including its prospectus, financial information, holdings, federal tax information and proxy voting information, visit the Fund's website included at the beginning of this report or scan the QR code below.

The Fund is distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC. Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

**Not FDIC or NCUA Insured • No Financial Institution Guarantee • May Lose Value**

![An image of a QR code that, when scanned, navigates the user to the following URL: https://www.columbiathreadneedleus.com/resources/literature](g38195g18l34.jpg)

Columbia Thermostat Fund℠ \| Institutional Class **\|** ASR235_08_(02/26) \|

------

#### Item 2. Code of Ethics.
The registrant has adopted a code of ethics (the "Code") that applies to the registrant's principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party. During the period covered by this report, there were not any amendments to a provision of the Code that relates to any element of the code of ethics definition enumerated in paragraph (b) of Item 2 of Form N-CSR. During the period covered by this report, there were no waivers, including any implicit waivers, from a provision of the Code that relates to one or more of the items set forth in paragraph (b) of Item 2 of Form N-CSR. A copy of the Code is attached hereto.

#### Item 3. Audit Committee Financial Expert.
The registrant's Board of Trustees has determined that J. Kevin Connaughton, Brian J. Gallagher, Douglas A. Hacker, David M. Moffett and Sandra L. Yeager qualify as "audit committee financial experts," as such term is defined in Form N-CSR. Mr. Connaughton, Mr. Gallagher, Mr. Hacker, Mr. Moffett and Ms. Yeager, are also each "independent" members of the Audit Committee pursuant to paragraph (a)(2) of Item 3 of Form N-CSR.

#### Item 4. Principal Accountant Fees and Services.
The registrant has engaged its principal accountant to perform audit services, audit-related services, tax services and other services during the past two fiscal years. The following table details the aggregate fees billed or expected to be billed for each of the last two fiscal years for the series of the relevant registrant whose reports to shareholders are included in this annual filing.

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Amount billed to the registrant<br>($)** | **Amount billed to the registrant<br>($)** | **Amount billed to the<br>registrant's investment advisor<br>($)** | **Amount billed to the<br>registrant's investment advisor<br>($)** |
|  | **December 31,<br>2025** | **December 31,<br>2024** | **December 31,<br>2025** | **December 31,<br>2024** |
|  Audit fees <sup>(a)</sup> | 120980 | 128174 | 0 | 0 |
|  Audit-related fees <sup>(b)</sup> | 0 | 0 | 0 | 0 |
|  Tax fees <sup>(c)</sup> | 73818 | 71053 | 0 | 0 |
|  All other fees <sup>(d)</sup> | 0 | 0 | 0 | 0 |
|  Non-audit fees <sup>(g)</sup> | 0 | 0 | 474000 | 581000 |

---

(a) Audit Fees include amounts related to the audit of the registrant's annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years.

(b) Audit-Related Fees include amounts for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant's financial statements and are not reported in Audit Fees above.

(c) Tax Fees include amounts for the review of annual tax returns, the review of required shareholder distribution calculations and typically include amounts for professional services by the principal accountant for tax compliance, tax advice, tax planning and foreign tax filings, if applicable.

------

(d) All Other Fees include amounts for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) above and typically include SOC-1 reviews.

(e)(1) Audit Committee Pre-Approval Policies and Procedures

The registrant's Audit Committee is required to pre-approve the engagement of the registrant's independent auditors to provide audit and non-audit services to the registrant and non-audit services to its investment adviser (excluding any sub-adviser whose role is primarily portfolio management and is sub-contracted or overseen by another investment adviser (the "Adviser") or any entity controlling, controlled by or under common control with the Adviser that provides ongoing services to the Fund (a "Control Affiliate") if the engagement relates directly to the operations and financial reporting of the registrant.

The Audit Committee has adopted a Policy for Engagement of Independent Auditors for Audit and Non-Audit Services (the "Policy"). The Policy sets forth the understanding of the Audit Committee regarding the engagement of the registrant's independent accountants to provide (i) audit and permissible audit-related, tax and other services to the registrant ("Fund Services"); (ii) non-audit services to the registrant's Adviser and any Control Affiliates, that relates directly to the operations and financial reporting of a Fund ("Fund-related Adviser Services"); and (iii) certain other audit and non-audit services to the registrant's Adviser and its Control Affiliates. A service will require specific pre-approval by the Audit Committee if it is to be provided by the Fund's independent auditor; provided, however, that pre-approval of non-audit services to the Fund, the Adviser or Control Affiliates may be waived if certain de minimis requirements set forth in the SEC's rules are met.

Under the Policy, the Audit Committee may delegate pre-approval authority to any pre-designated member or members who are independent board members. The member(s) to whom such authority is delegated must report, for informational purposes only, any pre-approval decisions to the Audit Committee at its next regular meeting. The Audit Committee's responsibilities with respect to the pre-approval of services performed by the independent auditor may not be delegated to management.

On an annual basis, at a regularly scheduled Audit Committee meeting, the Fund's Treasurer or other Fund officer shall submit to the Audit Committee a schedule of the types of Fund Services and Fund-related Adviser Services that are subject to specific pre-approval. This schedule will provide a description of each type of service that is subject to specific pre-approval, along with total projected fees for each service. The pre-approval will generally cover a one-year period. The Audit Committee will review and approve the types of services and the projected fees for the next one-year period and may add to, or subtract from, the list of pre-approved services from time to time, based on subsequent determinations. This specific approval acknowledges that the Audit Committee is in agreement with the specific types of services that the independent auditor will be permitted to perform and the projected fees for each service.

The Fund's Treasurer or other Fund officer shall report to the Audit Committee at each of its regular meetings regarding all Fund Services or Fund-related Adviser Services provided since the last such report was rendered, including a description of the services, by category, with forecasted fees for the annual reporting period, proposed changes requiring specific pre-approval and a description of services provided by the independent auditor, by category, with actual fees during the current reporting period.

(e)(2) None, or 0%, of the Audit-Related Fees, Tax Fees and All Other Fees paid by the Fund or affiliated entities relating directly to the operations and financial reporting of the Registrant disclosed above were approved by the audit committee pursuant to paragraphs (c)(7)(i)(C) of Rule 2-01 of Regulation S-X (which permits audit committee approval after the start of the engagement with respect to services other than audit, review or attest services, if certain conditions are satisfied).

------

(f) Not applicable.

(g) The aggregate non-audit fees billed by the registrant's accountant for services rendered to the registrant and rendered to the registrant's investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant.

(h) The registrant's Audit Committee of the Board of Trustees has considered whether the provision of non-audit services that were rendered to the registrant's adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X, is compatible with maintaining the principal accountant's independence.

(i) Not applicable.

(j) Not applicable.

#### Item 5. Audit Committee of Listed Registrants.
Not applicable.

#### Item 6. Investments.
(a) The registrant's "Schedule I – Investments in securities of unaffiliated issuers" (as set forth in 17 CFR 210.12-12) is included in Item 7 of this Form N-CSR.

(b) Not applicable.

#### Item 7. Financial Statements and Financial Highlights for Open-End Management Investment Companies.

------

![](g38195imgbe6089bc1.jpg)

**Annual Financial Statements and Additional Information**

December 31, 2025

Columbia Acorn<sup>®</sup> Fund

Columbia Acorn International<sup>®</sup>

Columbia Acorn International Select<sup>SM</sup>

Columbia Thermostat Fund<sup>SM</sup>

Columbia Acorn European Fund<sup>SM</sup>

---

| | | |
|:---|:---|:---|
| **Not FDIC or NCUA Insured** | **No Financial Institution Guarantee** | **May Lose Value** |

---

------

**Table of Contents**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| [Portfolio of Investments](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_POI-CommonContent-Date-339_1) | 3 |
| [Statement of Assets and Liabilities](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_FS-CommonContent-Date_1) | 22 |
| [Statement of Operations](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_FS-CommonContent-Date_5) | 26 |
| [Statement of Changes in Net Assets](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_FS-CommonContent-Date_7) | 28 |
| [Financial Highlights](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_FIHI-CommonContent-Date-339_1) | 34 |
| [Notes to Financial Statements](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_NTF-CommonContent-Date_1) | 52 |
| [Report of Independent Registered Public Accounting Firm](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_AUD-CommonContent-Date-339_1) | 66 |
| [Federal Income Tax Information](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_FITF-CommonContent-Date-339_1) | 67 |
| [Results of Meeting of Shareholders](#xx_3abbd3af-eece-4b9d-bb15-db86ddf6e407_ROMOS-CommonContent-Date-339_1) | 68 |

---

Columbia Acorn Trust \| 2025

------

Portfolio of Investments

Columbia Acorn<sup>®</sup> Fund, December 31, 2025

(Percentages represent value of investments compared to net assets)

**Investments in securities**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Common Stocks 98.3%** | **Common Stocks 98.3%** | **Common Stocks 98.3%** |
| **Issuer** | **Shares** | **Value ($)** |
| **Communication Services 0.8%** | **Communication Services 0.8%** | **Communication Services 0.8%** |
| **Media 0.8%** | **Media 0.8%** | **Media 0.8%** |
| NIQ Global Intelligence PLC<sup>(a)</sup> <br>| &nbsp;&nbsp; 1232928 | &nbsp;&nbsp; 20330983 |
| **Total Communication Services** | **Total Communication Services** | &nbsp;&nbsp; **20330983** |
| **Consumer Discretionary 11.0%** | **Consumer Discretionary 11.0%** | **Consumer Discretionary 11.0%** |
| **Automobile Components 1.3%** | **Automobile Components 1.3%** | **Automobile Components 1.3%** |
| Dorman Products, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 261776 | &nbsp;&nbsp; 32248185 |
| **Hotels, Restaurants & Leisure 4.2%** | **Hotels, Restaurants & Leisure 4.2%** | **Hotels, Restaurants & Leisure 4.2%** |
| Churchill Downs, Inc. | &nbsp;&nbsp; 455619 | &nbsp;&nbsp; 51840330 |
| Wingstop, Inc. | &nbsp;&nbsp; 206819 | &nbsp;&nbsp; 49324263 |
| Total |  | &nbsp;&nbsp; 101164593 |
| **Household Durables 5.0%** | **Household Durables 5.0%** | **Household Durables 5.0%** |
| Cavco Industries, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 74404 | &nbsp;&nbsp; 43953419 |
| SharkNinja, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 262983 | &nbsp;&nbsp; 29427798 |
| TopBuild Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 116923 | &nbsp;&nbsp; 48779106 |
| Total |  | &nbsp;&nbsp; 122160323 |
| **Specialty Retail 0.5%** | **Specialty Retail 0.5%** | **Specialty Retail 0.5%** |
| Five Below, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 64861 | &nbsp;&nbsp; 12217218 |
| **Total Consumer Discretionary** | **Total Consumer Discretionary** | &nbsp;&nbsp; **267790319** |
| **Consumer Staples 4.6%** | **Consumer Staples 4.6%** | **Consumer Staples 4.6%** |
| **Consumer Staples Distribution & Retail 2.2%** | **Consumer Staples Distribution & Retail 2.2%** | **Consumer Staples Distribution & Retail 2.2%** |
| BJ's Wholesale Club Holdings, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 378441 | &nbsp;&nbsp; 34071044 |
| Sprouts Farmers Market, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 248151 | &nbsp;&nbsp; 19770190 |
| Total |  | &nbsp;&nbsp; 53841234 |
| **Household Products 1.1%** | **Household Products 1.1%** | **Household Products 1.1%** |
| WD-40 Co. | &nbsp;&nbsp; 133886 | &nbsp;&nbsp; 26362153 |
| **Personal Care Products 1.3%** | **Personal Care Products 1.3%** | **Personal Care Products 1.3%** |
| elf Beauty, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 423227 | &nbsp;&nbsp; 32182181 |
| **Total Consumer Staples** | **Total Consumer Staples** | &nbsp;&nbsp; **112385568** |
| **Energy 1.9%** | **Energy 1.9%** | **Energy 1.9%** |
| **Energy Equipment & Services 0.9%** | **Energy Equipment & Services 0.9%** | **Energy Equipment & Services 0.9%** |
| TechnipFMC PLC | &nbsp;&nbsp; 492942 | &nbsp;&nbsp; 21965495 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Oil, Gas & Consumable Fuels 1.0%** | **Oil, Gas & Consumable Fuels 1.0%** | **Oil, Gas & Consumable Fuels 1.0%** |
| Antero Resources Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 355938 | &nbsp;&nbsp; 12265624 |
| EQT Corp. | &nbsp;&nbsp; 217207 | &nbsp;&nbsp; 11642295 |
| Total |  | &nbsp;&nbsp; 23907919 |
| **Total Energy** | **Total Energy** | &nbsp;&nbsp; **45873414** |
| **Financials 10.6%** | **Financials 10.6%** | **Financials 10.6%** |
| **Banks 1.7%** | **Banks 1.7%** | **Banks 1.7%** |
| Lakeland Financial Corp. | &nbsp;&nbsp; 214229 | &nbsp;&nbsp; 12223907 |
| Western Alliance Bancorp | &nbsp;&nbsp; 355644 | &nbsp;&nbsp; 29898991 |
| Total |  | &nbsp;&nbsp; 42122898 |
| **Capital Markets 7.5%** | **Capital Markets 7.5%** | **Capital Markets 7.5%** |
| Blue Owl Capital, Inc. | &nbsp;&nbsp; 1391042 | &nbsp;&nbsp; 20782167 |
| Carlyle Group, Inc. (The) | &nbsp;&nbsp; 841679 | &nbsp;&nbsp; 49751646 |
| GCM Grosvenor, Inc., Class A<sup>(b)</sup> <br>| &nbsp;&nbsp; 4428750 | &nbsp;&nbsp; 50133450 |
| Miami International Holdings, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 375067 | &nbsp;&nbsp; 16645473 |
| Moelis & Co., ADR, Class A | &nbsp;&nbsp; 355675 | &nbsp;&nbsp; 24449100 |
| StoneX Group, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 210427 | &nbsp;&nbsp; 20017921 |
| Total |  | &nbsp;&nbsp; 181779757 |
| **Insurance 1.4%** | **Insurance 1.4%** | **Insurance 1.4%** |
| Ryan Specialty Holdings, Inc., Class A | &nbsp;&nbsp; 647394 | &nbsp;&nbsp; 33424952 |
| **Total Financials** | **Total Financials** | &nbsp;&nbsp; **257327607** |
| **Health Care 20.9%** | **Health Care 20.9%** | **Health Care 20.9%** |
| **Biotechnology 6.5%** | **Biotechnology 6.5%** | **Biotechnology 6.5%** |
| Absci Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 2566842 | &nbsp;&nbsp; 8958279 |
| Annexon, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 1786958 | &nbsp;&nbsp; 8970529 |
| BridgeBio Pharma, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 283462 | &nbsp;&nbsp; 21682008 |
| Insmed, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 292031 | &nbsp;&nbsp; 50825075 |
| Madrigal Pharmaceuticals, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 13617 | &nbsp;&nbsp; 7929724 |
| Neurocrine Biosciences, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 116190 | &nbsp;&nbsp; 16479228 |
| Nuvalent, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 174598 | &nbsp;&nbsp; 17562813 |
| Revolution Medicines, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 247625 | &nbsp;&nbsp; 19723331 |
| Vaxcyte, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 153523 | &nbsp;&nbsp; 7083551 |
| Total |  | &nbsp;&nbsp; 159214538 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn<sup>®</sup> Fund, December 31, 2025

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Health Care Equipment & Supplies 4.7%** | **Health Care Equipment & Supplies 4.7%** | **Health Care Equipment & Supplies 4.7%** |
| Glaukos Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 277848 | &nbsp;&nbsp; 31371818 |
| iRhythm Technologies, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 69873 | &nbsp;&nbsp; 12398265 |
| Masimo Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 320808 | &nbsp;&nbsp; 41724289 |
| Penumbra, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 90129 | &nbsp;&nbsp; 28022007 |
| Total |  | &nbsp;&nbsp; 113516379 |
| **Health Care Providers & Services 5.4%** | **Health Care Providers & Services 5.4%** | **Health Care Providers & Services 5.4%** |
| Alignment Healthcare, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 1480873 | &nbsp;&nbsp; 29247242 |
| Billiontoone, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 79938 | &nbsp;&nbsp; 6542126 |
| Encompass Health Corp. | &nbsp;&nbsp; 287135 | &nbsp;&nbsp; 30476509 |
| Guardant Health, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 83871 | &nbsp;&nbsp; 8566584 |
| HealthEquity, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 445107 | &nbsp;&nbsp; 40776252 |
| Pennant Group, Inc. (The)<sup>(a)</sup> <br>| &nbsp;&nbsp; 584838 | &nbsp;&nbsp; 16463190 |
| Total |  | &nbsp;&nbsp; 132071903 |
| **Health Care Technology 0.9%** | **Health Care Technology 0.9%** | **Health Care Technology 0.9%** |
| Doximity, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 249335 | &nbsp;&nbsp; 11040554 |
| Phreesia, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 631324 | &nbsp;&nbsp; 10682002 |
| Total |  | &nbsp;&nbsp; 21722556 |
| **Life Sciences Tools & Services 2.4%** | **Life Sciences Tools & Services 2.4%** | **Life Sciences Tools & Services 2.4%** |
| Adaptive Biotechnologies Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 833223 | &nbsp;&nbsp; 13531541 |
| BioLife Solutions, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 696462 | &nbsp;&nbsp; 16840451 |
| Bio-Techne Corp. | &nbsp;&nbsp; 172270 | &nbsp;&nbsp; 10131199 |
| Charles River Laboratories International, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 12672 | &nbsp;&nbsp; 2527811 |
| DNA Script<sup>(a),(c),(d),(e)</sup> <br>| &nbsp;&nbsp; 1139 | &nbsp;&nbsp; 89683 |
| Fortrea Holdings, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 228661 | &nbsp;&nbsp; 3944402 |
| ICON PLC<sup>(a)</sup> <br>| &nbsp;&nbsp; 58336 | &nbsp;&nbsp; 10629986 |
| Total |  | &nbsp;&nbsp; 57695073 |
| **Pharmaceuticals 1.0%** | **Pharmaceuticals 1.0%** | **Pharmaceuticals 1.0%** |
| AtaiBeckley, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 909728 | &nbsp;&nbsp; 3720788 |
| Corcept Therapeutics, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 126858 | &nbsp;&nbsp; 4414658 |
| Crinetics Pharmaceuticals, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 148722 | &nbsp;&nbsp; 6923009 |
| Mind Medicine MindMed, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 419255 | &nbsp;&nbsp; 5613824 |
| Terns Pharmaceuticals, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 120565 | &nbsp;&nbsp; 4870826 |
| Total |  | &nbsp;&nbsp; 25543105 |
| **Total Health Care** | **Total Health Care** | &nbsp;&nbsp; **509763554** |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Industrials 27.2%** | **Industrials 27.2%** | **Industrials 27.2%** |
| **Aerospace & Defense 8.4%** | **Aerospace & Defense 8.4%** | **Aerospace & Defense 8.4%** |
| Aerovironment, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 120709 | &nbsp;&nbsp; 29198300 |
| Axon Enterprise, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 56304 | &nbsp;&nbsp; 31976731 |
| Beta Technologies, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 473817 | &nbsp;&nbsp; 13366377 |
| Curtiss-Wright Corp. | &nbsp;&nbsp; 66729 | &nbsp;&nbsp; 36785696 |
| Karman Holdings, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 163312 | &nbsp;&nbsp; 11949539 |
| Kratos Defense & Security Solutions, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 302224 | &nbsp;&nbsp; 22941824 |
| Moog, Inc., Class A | &nbsp;&nbsp; 44900 | &nbsp;&nbsp; 10935395 |
| VSE Corp. | &nbsp;&nbsp; 274746 | &nbsp;&nbsp; 47467866 |
| Total |  | &nbsp;&nbsp; 204621728 |
| **Building Products 2.4%** | **Building Products 2.4%** | **Building Products 2.4%** |
| Janus International Group, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 3345300 | &nbsp;&nbsp; 21878262 |
| Modine Manufacturing Co.<sup>(a)</sup> <br>| &nbsp;&nbsp; 278599 | &nbsp;&nbsp; 37195753 |
| Total |  | &nbsp;&nbsp; 59074015 |
| **Commercial Services & Supplies 0.6%** | **Commercial Services & Supplies 0.6%** | **Commercial Services & Supplies 0.6%** |
| Healthcare Services Group, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 784900 | &nbsp;&nbsp; 15007288 |
| **Construction & Engineering 3.4%** | **Construction & Engineering 3.4%** | **Construction & Engineering 3.4%** |
| MasTec, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 127639 | &nbsp;&nbsp; 27744889 |
| MYR Group, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 54984 | &nbsp;&nbsp; 12014004 |
| Sterling Infrastructure, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 136490 | &nbsp;&nbsp; 41797333 |
| Total |  | &nbsp;&nbsp; 81556226 |
| **Electrical Equipment 1.0%** | **Electrical Equipment 1.0%** | **Electrical Equipment 1.0%** |
| Bloom Energy Corp., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 288864 | &nbsp;&nbsp; 25099393 |
| **Machinery 3.9%** | **Machinery 3.9%** | **Machinery 3.9%** |
| Esab Corp. | &nbsp;&nbsp; 255766 | &nbsp;&nbsp; 28574177 |
| Mueller Water Products, Inc., Class A | &nbsp;&nbsp; 1095532 | &nbsp;&nbsp; 26095572 |
| SPX Technologies, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 206693 | &nbsp;&nbsp; 41351002 |
| Total |  | &nbsp;&nbsp; 96020751 |
| **Marine Transportation 0.8%** | **Marine Transportation 0.8%** | **Marine Transportation 0.8%** |
| Matson, Inc. | &nbsp;&nbsp; 148213 | &nbsp;&nbsp; 18311716 |
| **Professional Services 3.2%** | **Professional Services 3.2%** | **Professional Services 3.2%** |
| Parsons Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 607607 | &nbsp;&nbsp; 37550112 |
| Paylocity Holding Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 167076 | &nbsp;&nbsp; 25479090 |
| Willdan Group, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 137807 | &nbsp;&nbsp; 14285074 |
| Total |  | &nbsp;&nbsp; 77314276 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn<sup>®</sup> Fund, December 31, 2025

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Trading Companies & Distributors 3.5%** | **Trading Companies & Distributors 3.5%** | **Trading Companies & Distributors 3.5%** |
| Applied Industrial Technologies, Inc. | &nbsp;&nbsp; 111988 | &nbsp;&nbsp; 28755159 |
| FTAI Aviation Ltd. | &nbsp;&nbsp; 226826 | &nbsp;&nbsp; 44650698 |
| McGrath Rentcorp | &nbsp;&nbsp; 117334 | &nbsp;&nbsp; 12311857 |
| Total |  | &nbsp;&nbsp; 85717714 |
| **Total Industrials** | **Total Industrials** | &nbsp;&nbsp; **662723107** |
| **Information Technology 19.8%** | **Information Technology 19.8%** | **Information Technology 19.8%** |
| **Communications Equipment 1.5%** | **Communications Equipment 1.5%** | **Communications Equipment 1.5%** |
| InterDigital, Inc. | &nbsp;&nbsp; 30477 | &nbsp;&nbsp; 9703267 |
| Viavi Solutions, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 1429365 | &nbsp;&nbsp; 25471285 |
| Total |  | &nbsp;&nbsp; 35174552 |
| **Electronic Equipment, Instruments & Components 4.5%** | **Electronic Equipment, Instruments & Components 4.5%** | **Electronic Equipment, Instruments & Components 4.5%** |
| Celestica, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 183657 | &nbsp;&nbsp; 54290846 |
| Coherent Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 209402 | &nbsp;&nbsp; 38649327 |
| Ingram Micro Holding Corp. | &nbsp;&nbsp; 815196 | &nbsp;&nbsp; 17396282 |
| Total |  | &nbsp;&nbsp; 110336455 |
| **IT Services 0.9%** | **IT Services 0.9%** | **IT Services 0.9%** |
| Applied Digital Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 223784 | &nbsp;&nbsp; 5487184 |
| Globant SA<sup>(a)</sup> <br>| &nbsp;&nbsp; 261831 | &nbsp;&nbsp; 17115892 |
| Total |  | &nbsp;&nbsp; 22603076 |
| **Semiconductors & Semiconductor Equipment 4.7%** | **Semiconductors & Semiconductor Equipment 4.7%** | **Semiconductors & Semiconductor Equipment 4.7%** |
| Credo Technology Group Holding Ltd.<sup>(a)</sup> <br>| &nbsp;&nbsp; 127287 | &nbsp;&nbsp; 18315327 |
| Lattice Semiconductor Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 317863 | &nbsp;&nbsp; 23388360 |
| Marvell Technology, Inc. | &nbsp;&nbsp; 298398 | &nbsp;&nbsp; 25357862 |
| Semtech Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 421296 | &nbsp;&nbsp; 31045302 |
| SiTime Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 13575 | &nbsp;&nbsp; 4794554 |
| Tower Semiconductor Ltd.<sup>(a)</sup> <br>| &nbsp;&nbsp; 88489 | &nbsp;&nbsp; 10390378 |
| Total |  | &nbsp;&nbsp; 113291783 |
| **Software 8.2%** | **Software 8.2%** | **Software 8.2%** |
| Alkami Technology, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 551588 | &nbsp;&nbsp; 12725135 |
| Braze, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 388294 | &nbsp;&nbsp; 13314601 |
| CommVault Systems, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 59709 | &nbsp;&nbsp; 7485120 |
| Dynatrace, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 510994 | &nbsp;&nbsp; 22146480 |
| Gen Digital, Inc. | &nbsp;&nbsp; 934931 | &nbsp;&nbsp; 25420774 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| Gitlab, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 335015 | &nbsp;&nbsp; 12573113 |
| Hut 8 Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 143439 | &nbsp;&nbsp; 6589588 |
| Monday.com Ltd.<sup>(a)</sup> <br>| &nbsp;&nbsp; 106304 | &nbsp;&nbsp; 15686218 |
| SailPoint, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 820219 | &nbsp;&nbsp; 16593030 |
| SPS Commerce, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 109588 | &nbsp;&nbsp; 9767579 |
| Unity Software, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 235627 | &nbsp;&nbsp; 10407645 |
| Varonis Systems, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 376989 | &nbsp;&nbsp; 12365239 |
| Vertex, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 381861 | &nbsp;&nbsp; 7625764 |
| Workiva, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 110454 | &nbsp;&nbsp; 9526658 |
| Zeta Global Holdings Corp., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 895992 | &nbsp;&nbsp; 18233437 |
| Total |  | &nbsp;&nbsp; 200460381 |
| **Total Information Technology** | **Total Information Technology** | &nbsp;&nbsp; **481866247** |
| **Real Estate 1.5%** | **Real Estate 1.5%** | **Real Estate 1.5%** |
| **Real Estate Management & Development 1.5%** | **Real Estate Management & Development 1.5%** | **Real Estate Management & Development 1.5%** |
| Colliers International Group, Inc. | &nbsp;&nbsp; 247867 | &nbsp;&nbsp; 36438927 |
| **Total Real Estate** | **Total Real Estate** | &nbsp;&nbsp; **36438927** |
| Total Common Stocks <br>(Cost $1,976,251,331) | Total Common Stocks <br>(Cost $1,976,251,331) | &nbsp;&nbsp; **2394499726** |
| **Exchange-Traded Equity Funds 1.0%** | **Exchange-Traded Equity Funds 1.0%** | **Exchange-Traded Equity Funds 1.0%** |
|  | **Shares** | **Value ($)** |
| **International 0.3%** | **International 0.3%** | **International 0.3%** |
| Global X Blockchain ETF | &nbsp;&nbsp; 117737 | &nbsp;&nbsp; 7521040 |
| **Sector 0.7%** | **Sector 0.7%** | **Sector 0.7%** |
| State Street SPDR S&P Biotech ETF | &nbsp;&nbsp; 140554 | &nbsp;&nbsp; 17137749 |
| Total Exchange-Traded Equity Funds <br>(Cost $23,600,764) | Total Exchange-Traded Equity Funds <br>(Cost $23,600,764) | &nbsp;&nbsp; **24658789** |
| **Money Market Funds 0.6%** | **Money Market Funds 0.6%** | **Money Market Funds 0.6%** |
| Columbia Short-Term Cash Fund, 3.825%<sup>(b),(f)</sup> <br>| &nbsp;&nbsp; 15283690 | &nbsp;&nbsp; 15279105 |
| Total Money Market Funds <br>(Cost $15,275,242) | Total Money Market Funds <br>(Cost $15,275,242) | &nbsp;&nbsp; **15279105** |
| **Total Investments in Securities** <br>**(Cost: $2,015,127,337)** | **Total Investments in Securities** <br>**(Cost: $2,015,127,337)** | &nbsp;&nbsp; **2434437620** |
| **Other Assets & Liabilities, Net** |  | &nbsp;&nbsp; **1423099** |
| **Net Assets** | **Net Assets** | &nbsp;&nbsp; **2435860719** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn<sup>®</sup> Fund, December 31, 2025

**Notes to Portfolio of Investments** 

&nbsp;&nbsp;&nbsp;&nbsp;(a) Non-income producing investment.

&nbsp;&nbsp;&nbsp;&nbsp;(b) Under the Investment Company Act of 1940, an affiliated company is one in which the Fund owns 5% or more of the company's outstanding voting securities, or a company which is under common ownership or control with the Fund. The value of the holdings and transactions in these affiliated companies during the year ended December 31, 2025 are as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning** <br>**of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br>**unrealized** <br>**appreciation** <br>**(depreciation)($)**<br>| **End of** <br>**period($)**<br>| **Realized gain** <br>**(loss)($)**<br>| **Dividends($)** | **End of** <br>**period shares**<br>|
| Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% |
|  | 28748849 | &nbsp;&nbsp; 597196357 | &nbsp;&nbsp; (610664738)<br>| &nbsp;&nbsp; (1363)<br>| &nbsp;&nbsp; 15279105 | &nbsp;&nbsp; (2153)<br>| &nbsp;&nbsp; 1443441 | &nbsp;&nbsp; 15283690 |
| GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A | GCM Grosvenor, Inc., Class A |
|  | 60670978 | &nbsp;&nbsp; 1799376 | &nbsp;&nbsp; (8558880)<br>| &nbsp;&nbsp; (3778024)<br>| &nbsp;&nbsp; 50133450 | &nbsp;&nbsp; 623174 | &nbsp;&nbsp; 1268172 | &nbsp;&nbsp; 4428750 |
| Total | 89419827 |  |  | &nbsp;&nbsp; (3779387)<br>| &nbsp;&nbsp; 65412555 | &nbsp;&nbsp; 621021 | &nbsp;&nbsp; 2711613 |  |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(c) Represents fair value as determined in good faith under procedures approved by the Board of Trustees. At December 31, 2025, the total value of these securities amounted to $89,683, which represents less than 0.01% of total net assets.

&nbsp;&nbsp;&nbsp;&nbsp;(d) Denotes a restricted security, which is subject to legal or contractual restrictions on resale under federal securities laws. Disposal of a restricted investment may involve time-consuming negotiations and expenses, and prompt sale at an acceptable price may be difficult to achieve. Private placement securities are generally considered to be restricted, although certain of those securities may be traded between qualified institutional investors under the provisions of Section 4(a)(2) and Rule 144A. The Fund will not incur any registration costs upon such a trade. These securities are valued at fair value determined in good faith under consistently applied procedures approved by the Fund's Board of Trustees. At December 31, 2025, the total market value of these securities amounted to $89,683, which represents less than 0.01% of total net assets. Additional information on these securities is as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | |
|:---|:---|:---|:---|:---|
| **Security** | **Acquisition** <br>**Dates**<br>| **Shares** | **Cost ($)** | **Value ($)** |
| DNA Script | 10/01/2021 | &nbsp;&nbsp; 1139 | &nbsp;&nbsp; 993179 | &nbsp;&nbsp; 89683 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(e) Valuation based on significant unobservable inputs.

&nbsp;&nbsp;&nbsp;&nbsp;(f) The rate shown is the seven-day current annualized yield at December 31, 2025.

**Abbreviation Legend** 

ADR American Depositary Receipt

**Fair value measurements** 

The Fund categorizes its fair value measurements according to a three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by prioritizing that the most observable input be used when available. Observable inputs are those that market participants would use in pricing an investment based on market data obtained from sources independent of the reporting entity. Unobservable inputs are those that reflect the Fund's assumptions about the information market participants would use in pricing an investment. An investment's level within the fair value hierarchy is based on the lowest level of any input that is deemed significant to the asset's or liability's fair value measurement. The input levels are not necessarily an indication of the risk or liquidity associated with investments at that level. For example, certain U.S. government securities are generally high quality and liquid, however, they are reflected as Level 2 because the inputs used to determine fair value may not always be quoted prices in an active market.

Fair value inputs are summarized in the three broad levels listed below:

■

Level 1 — Valuations based on quoted prices for investments in active markets that the Fund has the ability to access at the measurement date. Valuation adjustments are not applied to Level 1 investments.

■

Level 2 — Valuations based on other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.).

■

Level 3 — Valuations based on significant unobservable inputs (including the Fund's own assumptions and judgment in determining the fair value of investments).

Inputs that are used in determining fair value of an investment may include price information, credit data, volatility statistics, and other factors. These inputs can be either observable or unobservable. The availability of observable inputs can vary between investments, and is affected by various factors such as the type of investment, and the volume and level of activity for that investment or similar investments in the marketplace. The inputs will be considered by the Investment Manager, along with any other relevant factors in the calculation of an investment's fair value. The Fund uses prices and inputs that are current as of the measurement date, which may include periods of market dislocations. During these periods, the availability of prices and inputs may be reduced for many investments. This condition could cause an investment to be reclassified between the various levels within the hierarchy.

Investments falling into the Level 3 category, if any, are primarily supported by quoted prices from brokers and dealers participating in the market for those investments. However, these may be classified as Level 3 investments due to lack of market transparency and corroboration to support these quoted prices. Additionally, valuation models may be used as the pricing source for any remaining investments classified as Level 3. These models may rely on one or more significant unobservable inputs and/or significant assumptions by the Investment Manager. Inputs used in valuations may include, but are not limited to, financial statement analysis, capital account balances, discount rates and estimated cash flows, and comparable company data.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn<sup>®</sup> Fund, December 31, 2025

**Fair value measurements (continued)**

The Fund's Board of Trustees (the Board) has designated the Investment Manager, through its Valuation Committee (the Committee), as valuation designee, responsible for determining the fair value of the assets of the Fund for which market quotations are not readily available using valuation procedures approved by the Board. The Committee consists of voting and non-voting members from various groups within the Investment Manager's organization, including operations and accounting, trading and investments, compliance, risk management and legal.

The Committee meets at least monthly to review and approve valuation matters, which may include a description of specific valuation determinations, data regarding pricing information received from approved pricing vendors and brokers and the results of Board-approved valuation policies and procedures (the Policies). The Policies address, among other things, instances when market quotations are or are not readily available, including recommendations of third party pricing vendors and a determination of appropriate pricing methodologies; events that require specific valuation determinations and assessment of fair value techniques; securities with a potential for stale pricing, including those that are illiquid, restricted, or in default; and the effectiveness of third party pricing vendors, including periodic reviews of vendors. The Committee meets more frequently, as needed, to discuss additional valuation matters, which may include the need to review back-testing results, review time-sensitive information or approve related valuation actions. Representatives of Columbia Management Investment Advisers, LLC report to the Board at each of its regularly scheduled meetings to discuss valuation matters and actions during the period, similar to those described earlier.

The following table is a summary of the inputs used to value the Fund's investments at December 31, 2025:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| **Investments in Securities** |  |  |  |  |
| Common Stocks |  |  |  |  |
| Communication Services | 20330983 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 20330983 |
| Consumer Discretionary | 267790319 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 267790319 |
| Consumer Staples | 112385568 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 112385568 |
| Energy | 45873414 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 45873414 |
| Financials | 257327607 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 257327607 |
| Health Care | 509673871 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 89683 | &nbsp;&nbsp;&nbsp;&nbsp; 509763554 |
| Industrials | 662723107 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 662723107 |
| Information Technology | 481866247 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 481866247 |
| Real Estate | 36438927 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 36438927 |
| Total Common Stocks | 2394410043 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 89683 | &nbsp;&nbsp;&nbsp;&nbsp; 2394499726 |
| Exchange-Traded Equity Funds | 24658789 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 24658789 |
| Money Market Funds | 15279105 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 15279105 |
| Total Investments in Securities | 2434347937 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 89683 | &nbsp;&nbsp;&nbsp;&nbsp; 2434437620 |

---

See the Portfolio of Investments for all investment classifications not indicated in the table.

The Fund does not hold any significant investments (greater than one percent of net assets) categorized as Level 3.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments

Columbia Acorn International<sup>®</sup>, December 31, 2025

(Percentages represent value of investments compared to net assets)

**Investments in securities**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Common Stocks 99.7%** | **Common Stocks 99.7%** | **Common Stocks 99.7%** |
| **Issuer** | **Shares** | **Value ($)** |
| **Australia 2.7%** | **Australia 2.7%** | **Australia 2.7%** |
| CAR Group Ltd. | &nbsp;&nbsp; 567683 | &nbsp;&nbsp; 11626873 |
| Pro Medicus Ltd. | &nbsp;&nbsp; 70767 | &nbsp;&nbsp; 10393068 |
| **Total** | **Total** | &nbsp;&nbsp; **22019941** |
| **Canada 0.5%** | **Canada 0.5%** | **Canada 0.5%** |
| CCL Industries, Inc., Class B | &nbsp;&nbsp; 64213 | &nbsp;&nbsp; 4056149 |
| **China 0.9%** | **China 0.9%** | **China 0.9%** |
| Silergy Corp. | &nbsp;&nbsp; 1138000 | &nbsp;&nbsp; 6901660 |
| **Finland 3.7%** | **Finland 3.7%** | **Finland 3.7%** |
| Konecranes OYJ | &nbsp;&nbsp; 139832 | &nbsp;&nbsp; 15312374 |
| Valmet OYJ | &nbsp;&nbsp; 442703 | &nbsp;&nbsp; 14630341 |
| **Total** | **Total** | &nbsp;&nbsp; **29942715** |
| **France 2.9%** | **France 2.9%** | **France 2.9%** |
| Gaztransport Et Technigaz SA | &nbsp;&nbsp; 63347 | &nbsp;&nbsp; 11623333 |
| Robertet SA | &nbsp;&nbsp; 5645 | &nbsp;&nbsp; 5824656 |
| Virbac SA | &nbsp;&nbsp; 13867 | &nbsp;&nbsp; 5814471 |
| **Total** | **Total** | &nbsp;&nbsp; **23262460** |
| **Germany 6.4%** | **Germany 6.4%** | **Germany 6.4%** |
| Atoss Software SE | &nbsp;&nbsp; 61451 | &nbsp;&nbsp; 8303207 |
| CTS Eventim AG & Co. KGaA | &nbsp;&nbsp; 170821 | &nbsp;&nbsp; 15637355 |
| Hypoport SE<sup>(a)</sup> <br>| &nbsp;&nbsp; 50632 | &nbsp;&nbsp; 7559734 |
| Nemetschek SE | &nbsp;&nbsp; 146401 | &nbsp;&nbsp; 15839162 |
| Renk Group AG | &nbsp;&nbsp; 64836 | &nbsp;&nbsp; 4040667 |
| **Total** | **Total** | &nbsp;&nbsp; **51380125** |
| **Greece 1.7%** | **Greece 1.7%** | **Greece 1.7%** |
| National Bank of Greece SA | &nbsp;&nbsp; 914195 | &nbsp;&nbsp; 13943716 |
| **Ireland 2.6%** | **Ireland 2.6%** | **Ireland 2.6%** |
| Bank of Ireland Group PLC | &nbsp;&nbsp; 1089587 | &nbsp;&nbsp; 20838686 |
| **Italy 3.3%** | **Italy 3.3%** | **Italy 3.3%** |
| Carel Industries SpA | &nbsp;&nbsp; 241694 | &nbsp;&nbsp; 6944320 |
| Prysmian SpA | &nbsp;&nbsp; 194146 | &nbsp;&nbsp; 19367491 |
| **Total** | **Total** | &nbsp;&nbsp; **26311811** |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Japan 39.2%** | **Japan 39.2%** | **Japan 39.2%** |
| Asics Corp. | &nbsp;&nbsp; 240200 | &nbsp;&nbsp; 5766354 |
| BayCurrent, Inc. | &nbsp;&nbsp; 116500 | &nbsp;&nbsp; 4830521 |
| Capcom Co., Ltd. | &nbsp;&nbsp; 840500 | &nbsp;&nbsp; 19524010 |
| Disco Corp. | &nbsp;&nbsp; 48800 | &nbsp;&nbsp; 14867519 |
| DMG Mori Co., Ltd. | &nbsp;&nbsp; 312400 | &nbsp;&nbsp; 5264455 |
| Gunma Bank Ltd. (The) | &nbsp;&nbsp; 748400 | &nbsp;&nbsp; 8268813 |
| Ibiden Co., Ltd. | &nbsp;&nbsp; 170200 | &nbsp;&nbsp; 7351262 |
| Kokusai Electric Corp. | &nbsp;&nbsp; 562500 | &nbsp;&nbsp; 19671834 |
| Kraftia Corp. | &nbsp;&nbsp; 344600 | &nbsp;&nbsp; 16947838 |
| Kyoritsu Maintenance Co., Ltd. | &nbsp;&nbsp; 607100 | &nbsp;&nbsp; 10822305 |
| MatsukiyoCocokara & Co. | &nbsp;&nbsp; 538300 | &nbsp;&nbsp; 9319903 |
| Modec, Inc. | &nbsp;&nbsp; 60600 | &nbsp;&nbsp; 4600424 |
| Nippon Sanso Holdings Corp. | &nbsp;&nbsp; 432900 | &nbsp;&nbsp; 12932489 |
| Nissin Foods Holdings Co., Ltd. | &nbsp;&nbsp; 363100 | &nbsp;&nbsp; 6749372 |
| Niterra Co., Ltd. | &nbsp;&nbsp; 475400 | &nbsp;&nbsp; 20945306 |
| Nomura Real Estate Holdings, Inc. | &nbsp;&nbsp; 2734500 | &nbsp;&nbsp; 16881042 |
| Omron Corp. | &nbsp;&nbsp; 409300 | &nbsp;&nbsp; 10355244 |
| Open House Co., Ltd. | &nbsp;&nbsp; 82200 | &nbsp;&nbsp; 4825087 |
| Recruit Holdings Co., Ltd. | &nbsp;&nbsp; 181400 | &nbsp;&nbsp; 10193153 |
| Renesas Electronics Corp.<sup>(a)</sup> <br>| &nbsp;&nbsp; 863100 | &nbsp;&nbsp; 11821753 |
| Sanwa Holdings Corp. | &nbsp;&nbsp; 495050 | &nbsp;&nbsp; 12890207 |
| Sekisui Chemical Co., Ltd. | &nbsp;&nbsp; 720000 | &nbsp;&nbsp; 12108430 |
| Shimadzu Corp. | &nbsp;&nbsp; 141000 | &nbsp;&nbsp; 3753647 |
| Simplex Holdings, Inc. | &nbsp;&nbsp; 2400400 | &nbsp;&nbsp; 16122847 |
| Suntory Beverage & Food Ltd. | &nbsp;&nbsp; 463600 | &nbsp;&nbsp; 13942103 |
| Taisei Corp. | &nbsp;&nbsp; 253400 | &nbsp;&nbsp; 24014952 |
| Yaskawa Electric Corp. | &nbsp;&nbsp; 354900 | &nbsp;&nbsp; 10789452 |
| **Total** | **Total** | &nbsp;&nbsp; **315560322** |
| **Jersey 0.9%** | **Jersey 0.9%** | **Jersey 0.9%** |
| Yellow Cake PLC<sup>(a)</sup> <br>| &nbsp;&nbsp; 890470 | &nbsp;&nbsp; 7049728 |
| **Luxembourg 0.8%** | **Luxembourg 0.8%** | **Luxembourg 0.8%** |
| CVC Capital Partners PLC<sup>(b)</sup> <br>| &nbsp;&nbsp; 391081 | &nbsp;&nbsp; 6549636 |
| **Mexico 0.6%** | **Mexico 0.6%** | **Mexico 0.6%** |
| Corporación Inmobiliaria Vesta SAB de CV | &nbsp;&nbsp; 1582900 | &nbsp;&nbsp; 4841657 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn International<sup>®</sup>, December 31, 2025

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Netherlands 2.1%** | **Netherlands 2.1%** | **Netherlands 2.1%** |
| BE Semiconductor Industries NV | &nbsp;&nbsp; 108708 | &nbsp;&nbsp; 16994981 |
| **New Zealand 2.2%** | **New Zealand 2.2%** | **New Zealand 2.2%** |
| Fisher & Paykel Healthcare Corp., Ltd. | &nbsp;&nbsp; 819257 | &nbsp;&nbsp; 17799945 |
| **Sweden 4.7%** | **Sweden 4.7%** | **Sweden 4.7%** |
| AddTech AB, B Shares | &nbsp;&nbsp; 315479 | &nbsp;&nbsp; 11110732 |
| Hexagon AB, Class B | &nbsp;&nbsp; 1545048 | &nbsp;&nbsp; 18198663 |
| Munters Group AB | &nbsp;&nbsp; 478905 | &nbsp;&nbsp; 8783235 |
| **Total** | **Total** | &nbsp;&nbsp; **38092630** |
| **Switzerland 5.1%** | **Switzerland 5.1%** | **Switzerland 5.1%** |
| Belimo Holding AG, Registered Shares | &nbsp;&nbsp; 12549 | &nbsp;&nbsp; 12261170 |
| Inficon Holding AG, Registered Shares | &nbsp;&nbsp; 60601 | &nbsp;&nbsp; 7498330 |
| Interroll Holding AG, Registered Shares | &nbsp;&nbsp; 1427 | &nbsp;&nbsp; 3948375 |
| Kardex Holding AG | &nbsp;&nbsp; 24629 | &nbsp;&nbsp; 8529723 |
| VAT Group AG | &nbsp;&nbsp; 19160 | &nbsp;&nbsp; 9198715 |
| **Total** | **Total** | &nbsp;&nbsp; **41436313** |
| **United Kingdom 16.1%** | **United Kingdom 16.1%** | **United Kingdom 16.1%** |
| Ashtead Group PLC | &nbsp;&nbsp; 222079 | &nbsp;&nbsp; 15141169 |
| Auto Trader Group PLC | &nbsp;&nbsp; 1459202 | &nbsp;&nbsp; 11512172 |
| Babcock International Group PLC | &nbsp;&nbsp; 1053570 | &nbsp;&nbsp; 17557544 |
| Baltic Classifieds Group PLC | &nbsp;&nbsp; 2676145 | &nbsp;&nbsp; 7322839 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| ConvaTec Group PLC | &nbsp;&nbsp; 4036411 | &nbsp;&nbsp; 13178535 |
| Halma PLC | &nbsp;&nbsp; 457501 | &nbsp;&nbsp; 21715226 |
| Howden Joinery Group PLC | &nbsp;&nbsp; 525766 | &nbsp;&nbsp; 5884127 |
| ICG PLC | &nbsp;&nbsp; 623353 | &nbsp;&nbsp; 17189707 |
| Rightmove PLC | &nbsp;&nbsp; 1307674 | &nbsp;&nbsp; 9136333 |
| Safestore Holdings PLC | &nbsp;&nbsp; 1099285 | &nbsp;&nbsp; 10905910 |
| **Total** | **Total** | &nbsp;&nbsp; **129543562** |
| **United States 3.3%** | **United States 3.3%** | **United States 3.3%** |
| CRH PLC | &nbsp;&nbsp; 138047 | &nbsp;&nbsp; 17153927 |
| Interparfums, Inc. | &nbsp;&nbsp; 116341 | &nbsp;&nbsp; 9869207 |
| **Total** | **Total** | &nbsp;&nbsp; **27023134** |
| Total Common Stocks <br>(Cost $583,483,523) | Total Common Stocks <br>(Cost $583,483,523) | &nbsp;&nbsp; **803549171** |
| **Money Market Funds 0.5%** | **Money Market Funds 0.5%** | **Money Market Funds 0.5%** |
|  | **Shares** | **Value ($)** |
| Columbia Short-Term Cash Fund, 3.825%<sup>(c),(d)</sup> <br>| &nbsp;&nbsp; 4176926 | &nbsp;&nbsp; 4175673 |
| Total Money Market Funds <br>(Cost $4,175,497) | Total Money Market Funds <br>(Cost $4,175,497) | &nbsp;&nbsp; **4175673** |
| **Total Investments in Securities** <br>**(Cost $587,659,020)** | **Total Investments in Securities** <br>**(Cost $587,659,020)** | &nbsp;&nbsp; **807724844** |
| **Other Assets & Liabilities, Net** |  | &nbsp;&nbsp; **(1828983)**<br>|
| **Net Assets** | **Net Assets** | &nbsp;&nbsp; **$805895861** |

---

**Notes to Portfolio of Investments** 

&nbsp;&nbsp;&nbsp;&nbsp;(a) Non-income producing investment.

&nbsp;&nbsp;&nbsp;&nbsp;(b) Represents privately placed and other securities and instruments exempt from Securities and Exchange Commission registration (collectively, private placements), such as Section 4(a)(2) and Rule 144A eligible securities, which are often sold only to qualified institutional buyers. At December 31, 2025, the total value of these securities amounted to $6,549,636, which represents 0.81% of total net assets.

&nbsp;&nbsp;&nbsp;&nbsp;(c) The rate shown is the seven-day current annualized yield at December 31, 2025.

&nbsp;&nbsp;&nbsp;&nbsp;(d) Under the Investment Company Act of 1940, an affiliated company is one in which the Fund owns 5% or more of the company's outstanding voting securities, or a company which is under common ownership or control with the Fund. The value of the holdings and transactions in these affiliated companies during the year ended December 31, 2025 are as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning** <br>**of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br>**unrealized** <br>**appreciation** <br>**(depreciation)($)**<br>| **End of** <br>**period($)**<br>| **Realized gain** <br>**(loss)($)**<br>| **Dividends($)** | **End of** <br>**period shares**<br>|
| Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% |
|  | 3715484 | &nbsp;&nbsp; 203705268 | &nbsp;&nbsp; (203245255)<br>| &nbsp;&nbsp; 176 | &nbsp;&nbsp; 4175673 | &nbsp;&nbsp; (1405)<br>| &nbsp;&nbsp; 336167 | &nbsp;&nbsp; 4176926 |

---

**Fair value measurements** 

The Fund categorizes its fair value measurements according to a three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by prioritizing that the most observable input be used when available. Observable inputs are those that market participants would use in pricing an investment based on market data obtained from sources independent of the reporting entity. Unobservable inputs are those that reflect the Fund's assumptions about the information market participants would use in pricing an investment. An investment's level within the fair value hierarchy is based on the lowest level of any input that is deemed significant to

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn International<sup>®</sup>, December 31, 2025

**Fair value measurements (continued)**

the asset's or liability's fair value measurement. The input levels are not necessarily an indication of the risk or liquidity associated with investments at that level. For example, certain U.S. government securities are generally high quality and liquid, however, they are reflected as Level 2 because the inputs used to determine fair value may not always be quoted prices in an active market.

Fair value inputs are summarized in the three broad levels listed below:

■

Level 1 — Valuations based on quoted prices for investments in active markets that the Fund has the ability to access at the measurement date. Valuation adjustments are not applied to Level 1 investments.

■

Level 2 — Valuations based on other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.).

■

Level 3 — Valuations based on significant unobservable inputs (including the Fund's own assumptions and judgment in determining the fair value of investments).

Inputs that are used in determining fair value of an investment may include price information, credit data, volatility statistics, and other factors. These inputs can be either observable or unobservable. The availability of observable inputs can vary between investments, and is affected by various factors such as the type of investment, and the volume and level of activity for that investment or similar investments in the marketplace. The inputs will be considered by the Investment Manager, along with any other relevant factors in the calculation of an investment's fair value. The Fund uses prices and inputs that are current as of the measurement date, which may include periods of market dislocations. During these periods, the availability of prices and inputs may be reduced for many investments. This condition could cause an investment to be reclassified between the various levels within the hierarchy.

Values of foreign equity securities actively traded in markets where there is a significant delay in the local close relative to the New York Stock Exchange may include an adjustment to reflect the impact of market movements following the close of local trading, as described in Note 2 to the financial statements – Security valuation. When such adjustments have been made, the foreign equity securities are classified as Level 2.

Investments falling into the Level 3 category, if any, are primarily supported by quoted prices from brokers and dealers participating in the market for those investments. However, these may be classified as Level 3 investments due to lack of market transparency and corroboration to support these quoted prices. Additionally, valuation models may be used as the pricing source for any remaining investments classified as Level 3. These models may rely on one or more significant unobservable inputs and/or significant assumptions by the Investment Manager. Inputs used in valuations may include, but are not limited to, financial statement analysis, capital account balances, discount rates and estimated cash flows, and comparable company data.

The Fund's Board of Trustees (the Board) has designated the Investment Manager, through its Valuation Committee (the Committee), as valuation designee, responsible for determining the fair value of the assets of the Fund for which market quotations are not readily available using valuation procedures approved by the Board. The Committee consists of voting and non-voting members from various groups within the Investment Manager's organization, including operations and accounting, trading and investments, compliance, risk management and legal.

The Committee meets at least monthly to review and approve valuation matters, which may include a description of specific valuation determinations, data regarding pricing information received from approved pricing vendors and brokers and the results of Board-approved valuation policies and procedures (the Policies). The Policies address, among other things, instances when market quotations are or are not readily available, including recommendations of third party pricing vendors and a determination of appropriate pricing methodologies; events that require specific valuation determinations and assessment of fair value techniques; securities with a potential for stale pricing, including those that are illiquid, restricted, or in default; and the effectiveness of third party pricing vendors, including periodic reviews of vendors. The Committee meets more frequently, as needed, to discuss additional valuation matters, which may include the need to review back-testing results, review time-sensitive information or approve related valuation actions. Representatives of Columbia Management Investment Advisers, LLC report to the Board at each of its regularly scheduled meetings to discuss valuation matters and actions during the period, similar to those described earlier.

The following table is a summary of the inputs used to value the Fund's investments at December 31, 2025:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| **Investments in Securities** |  |  |  |  |
| Common Stocks |  |  |  |  |
| Australia |  | &nbsp;&nbsp;&nbsp;&nbsp; 22019941 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 22019941 |
| Canada | 4056149 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4056149 |
| China |  | &nbsp;&nbsp;&nbsp;&nbsp; 6901660 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 6901660 |
| Finland |  | &nbsp;&nbsp;&nbsp;&nbsp; 29942715 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 29942715 |
| France | 5824656 | &nbsp;&nbsp;&nbsp;&nbsp; 17437804 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 23262460 |
| Germany |  | &nbsp;&nbsp;&nbsp;&nbsp; 51380125 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 51380125 |
| Greece |  | &nbsp;&nbsp;&nbsp;&nbsp; 13943716 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 13943716 |
| Ireland |  | &nbsp;&nbsp;&nbsp;&nbsp; 20838686 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 20838686 |
| Italy |  | &nbsp;&nbsp;&nbsp;&nbsp; 26311811 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 26311811 |
| Japan | 9319903 | &nbsp;&nbsp;&nbsp;&nbsp; 306240419 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 315560322 |
| Jersey |  | &nbsp;&nbsp;&nbsp;&nbsp; 7049728 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 7049728 |
| Luxembourg |  | &nbsp;&nbsp;&nbsp;&nbsp; 6549636 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 6549636 |
| Mexico | 4841657 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4841657 |
| Netherlands |  | &nbsp;&nbsp;&nbsp;&nbsp; 16994981 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 16994981 |
| New Zealand |  | &nbsp;&nbsp;&nbsp;&nbsp; 17799945 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 17799945 |
| Sweden |  | &nbsp;&nbsp;&nbsp;&nbsp; 38092630 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 38092630 |
| Switzerland |  | &nbsp;&nbsp;&nbsp;&nbsp; 41436313 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 41436313 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn International<sup>®</sup>, December 31, 2025

**Fair value measurements (continued)**

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| United Kingdom | 18228749 | &nbsp;&nbsp;&nbsp;&nbsp; 111314813 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 129543562 |
| United States | 9869207 | &nbsp;&nbsp;&nbsp;&nbsp; 17153927 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 27023134 |
| Total Common Stocks | 52140321 | &nbsp;&nbsp;&nbsp;&nbsp; 751408850 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 803549171 |
| Money Market Funds | 4175673 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4175673 |
| Total Investments in Securities | 56315994 | &nbsp;&nbsp;&nbsp;&nbsp; 751408850 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 807724844 |

---

See the Portfolio of Investments for all investment classifications not indicated in the table.

The Fund's assets assigned to the Level 2 input category are generally valued using the market approach, in which a security's value is determined through reference to prices and information from market transactions for similar or identical assets. These assets include certain foreign securities for which a third party statistical pricing service may be employed for purposes of fair market valuation. The model utilized by such third party statistical pricing service takes into account a security's correlation to available market data including relevant general and sector indices, currency fluctuations, depositary receipts, and futures, as applicable.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments

Columbia Acorn International Select<sup>SM</sup>, December 31, 2025

(Percentages represent value of investments compared to net assets)

**Investments in securities**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Common Stocks 99.2%** | **Common Stocks 99.2%** | **Common Stocks 99.2%** |
| **Issuer** | **Shares** | **Value ($)** |
| **Australia 1.1%** | **Australia 1.1%** | **Australia 1.1%** |
| CSL Ltd. | &nbsp;&nbsp; 19170 | &nbsp;&nbsp; 2206112 |
| **Canada 0.6%** | **Canada 0.6%** | **Canada 0.6%** |
| Shopify, Inc., Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 6966 | &nbsp;&nbsp; 1121625 |
| **Denmark 1.5%** | **Denmark 1.5%** | **Denmark 1.5%** |
| Novo Nordisk A/S, Class B | &nbsp;&nbsp; 59175 | &nbsp;&nbsp; 3001266 |
| **Finland 1.0%** | **Finland 1.0%** | **Finland 1.0%** |
| Konecranes OYJ | &nbsp;&nbsp; 17648 | &nbsp;&nbsp; 1932553 |
| **France 18.1%** | **France 18.1%** | **France 18.1%** |
| Airbus Group SE | &nbsp;&nbsp; 26349 | &nbsp;&nbsp; 6118870 |
| Cie de Saint-Gobain SA | &nbsp;&nbsp; 40600 | &nbsp;&nbsp; 4128691 |
| EssilorLuxottica SA | &nbsp;&nbsp; 11484 | &nbsp;&nbsp; 3631217 |
| Legrand SA | &nbsp;&nbsp; 13158 | &nbsp;&nbsp; 1956105 |
| LVMH Moet Hennessy Louis Vuitton SE | &nbsp;&nbsp; 8139 | &nbsp;&nbsp; 6134655 |
| Publicis Groupe SA | &nbsp;&nbsp; 44604 | &nbsp;&nbsp; 4632024 |
| Schneider Electric SE | &nbsp;&nbsp; 29845 | &nbsp;&nbsp; 8164854 |
| TotalEnergies SE | &nbsp;&nbsp; 21939 | &nbsp;&nbsp; 1430379 |
| **Total** | **Total** | &nbsp;&nbsp; **36196795** |
| **Germany 7.6%** | **Germany 7.6%** | **Germany 7.6%** |
| Adidas AG | &nbsp;&nbsp; 22562 | &nbsp;&nbsp; 4464704 |
| Deutsche Telekom AG, Registered Shares | &nbsp;&nbsp; 123264 | &nbsp;&nbsp; 4012374 |
| Nemetschek SE | &nbsp;&nbsp; 25067 | &nbsp;&nbsp; 2712005 |
| Renk Group AG | &nbsp;&nbsp; 15769 | &nbsp;&nbsp; 982745 |
| SAP SE | &nbsp;&nbsp; 12455 | &nbsp;&nbsp; 3026173 |
| **Total** | **Total** | &nbsp;&nbsp; **15198001** |
| **Ireland 2.6%** | **Ireland 2.6%** | **Ireland 2.6%** |
| Bank of Ireland Group PLC | &nbsp;&nbsp; 268505 | &nbsp;&nbsp; 5135240 |
| **Italy 1.8%** | **Italy 1.8%** | **Italy 1.8%** |
| Prysmian SpA | &nbsp;&nbsp; 36742 | &nbsp;&nbsp; 3665285 |
| **Japan 27.9%** | **Japan 27.9%** | **Japan 27.9%** |
| BayCurrent, Inc. | &nbsp;&nbsp; 26300 | &nbsp;&nbsp; 1090495 |
| Capcom Co., Ltd. | &nbsp;&nbsp; 212900 | &nbsp;&nbsp; 4945463 |
| Daikin Industries Ltd. | &nbsp;&nbsp; 20000 | &nbsp;&nbsp; 2557836 |
| Disco Corp. | &nbsp;&nbsp; 12700 | &nbsp;&nbsp; 3869211 |
| Gunma Bank Ltd. (The) | &nbsp;&nbsp; 273500 | &nbsp;&nbsp; 3021807 |
| Ibiden Co., Ltd. | &nbsp;&nbsp; 41200 | &nbsp;&nbsp; 1779507 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| Kokusai Electric Corp. | &nbsp;&nbsp; 100600 | &nbsp;&nbsp; 3518198 |
| MatsukiyoCocokara & Co. | &nbsp;&nbsp; 129100 | &nbsp;&nbsp; 2235184 |
| Niterra Co., Ltd. | &nbsp;&nbsp; 98300 | &nbsp;&nbsp; 4330929 |
| Nomura Real Estate Holdings, Inc. | &nbsp;&nbsp; 322000 | &nbsp;&nbsp; 1987821 |
| Omron Corp. | &nbsp;&nbsp; 98800 | &nbsp;&nbsp; 2499629 |
| ORIX Corp. | &nbsp;&nbsp; 69500 | &nbsp;&nbsp; 2032686 |
| Recruit Holdings Co., Ltd. | &nbsp;&nbsp; 59500 | &nbsp;&nbsp; 3343399 |
| Sekisui Chemical Co., Ltd. | &nbsp;&nbsp; 88200 | &nbsp;&nbsp; 1483283 |
| Shimadzu Corp. | &nbsp;&nbsp; 54900 | &nbsp;&nbsp; 1461526 |
| Suntory Beverage & Food Ltd. | &nbsp;&nbsp; 98100 | &nbsp;&nbsp; 2950216 |
| Taisei Corp. | &nbsp;&nbsp; 65200 | &nbsp;&nbsp; 6179064 |
| Tokyo Electron Ltd. | &nbsp;&nbsp; 18400 | &nbsp;&nbsp; 4098184 |
| Yaskawa Electric Corp. | &nbsp;&nbsp; 80700 | &nbsp;&nbsp; 2453392 |
| **Total** | **Total** | &nbsp;&nbsp; **55837830** |
| **Netherlands 3.6%** | **Netherlands 3.6%** | **Netherlands 3.6%** |
| ASML Holding NV | &nbsp;&nbsp; 6671 | &nbsp;&nbsp; 7188137 |
| **New Zealand 1.0%** | **New Zealand 1.0%** | **New Zealand 1.0%** |
| Fisher & Paykel Healthcare Corp., Ltd. | &nbsp;&nbsp; 89689 | &nbsp;&nbsp; 1948667 |
| **Spain 2.8%** | **Spain 2.8%** | **Spain 2.8%** |
| Industria de Diseno Textil SA | &nbsp;&nbsp; 83602 | &nbsp;&nbsp; 5514779 |
| **Switzerland 5.7%** | **Switzerland 5.7%** | **Switzerland 5.7%** |
| Belimo Holding AG, Registered Shares | &nbsp;&nbsp; 1722 | &nbsp;&nbsp; 1682503 |
| Interroll Holding AG, Registered Shares | &nbsp;&nbsp; 323 | &nbsp;&nbsp; 893711 |
| Lonza Group AG, Registered Shares | &nbsp;&nbsp; 5084 | &nbsp;&nbsp; 3427734 |
| Nestlé SA, Registered Shares | &nbsp;&nbsp; 36109 | &nbsp;&nbsp; 3584147 |
| VAT Group AG | &nbsp;&nbsp; 3930 | &nbsp;&nbsp; 1886793 |
| **Total** | **Total** | &nbsp;&nbsp; **11474888** |
| **United Kingdom 21.6%** | **United Kingdom 21.6%** | **United Kingdom 21.6%** |
| 3i Group PLC | &nbsp;&nbsp; 132612 | &nbsp;&nbsp; 5814882 |
| Ashtead Group PLC | &nbsp;&nbsp; 65379 | &nbsp;&nbsp; 4457488 |
| Auto Trader Group PLC | &nbsp;&nbsp; 177233 | &nbsp;&nbsp; 1398255 |
| Babcock International Group PLC | &nbsp;&nbsp; 161224 | &nbsp;&nbsp; 2686767 |
| BT Group PLC | &nbsp;&nbsp; 1857140 | &nbsp;&nbsp; 4600956 |
| ConvaTec Group PLC | &nbsp;&nbsp; 665130 | &nbsp;&nbsp; 2171592 |
| Halma PLC | &nbsp;&nbsp; 44904 | &nbsp;&nbsp; 2131363 |
| ICG PLC | &nbsp;&nbsp; 150106 | &nbsp;&nbsp; 4139353 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn International Select<sup>SM</sup>, December 31, 2025

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| London Stock Exchange Group PLC | &nbsp;&nbsp; 29163 | &nbsp;&nbsp; 3507974 |
| Reckitt Benckiser Group PLC | &nbsp;&nbsp; 44362 | &nbsp;&nbsp; 3589744 |
| Rightmove PLC | &nbsp;&nbsp; 235662 | &nbsp;&nbsp; 1646501 |
| Rio Tinto PLC | &nbsp;&nbsp; 23486 | &nbsp;&nbsp; 1891822 |
| Standard Chartered PLC | &nbsp;&nbsp; 210961 | &nbsp;&nbsp; 5147542 |
| **Total** | **Total** | &nbsp;&nbsp; **43184239** |
| **United States 2.3%** | **United States 2.3%** | **United States 2.3%** |
| CRH PLC | &nbsp;&nbsp; 36450 | &nbsp;&nbsp; 4529332 |
| Total Common Stocks <br>(Cost $158,498,106) | Total Common Stocks <br>(Cost $158,498,106) | &nbsp;&nbsp; **198134749** |

---

---

| | | |
|:---|:---|:---|
| **Money Market Funds 1.2%** | **Money Market Funds 1.2%** | **Money Market Funds 1.2%** |
|  | **Shares** | **Value ($)** |
| Columbia Short-Term Cash Fund, 3.825%<sup>(b),(c)</sup> <br>| &nbsp;&nbsp; 2433514 | &nbsp;&nbsp; 2432784 |
| Total Money Market Funds <br>(Cost $2,432,754) | Total Money Market Funds <br>(Cost $2,432,754) | &nbsp;&nbsp; **2432784** |
| **Total Investments in Securities** <br>**(Cost $160,930,860)** | **Total Investments in Securities** <br>**(Cost $160,930,860)** | &nbsp;&nbsp; **200567533** |
| **Other Assets & Liabilities, Net** |  | &nbsp;&nbsp; **(728260)**<br>|
| **Net Assets** | **Net Assets** | &nbsp;&nbsp; **$199839273** |

---

**Notes to Portfolio of Investments** 

&nbsp;&nbsp;&nbsp;&nbsp;(a) Non-income producing investment.

&nbsp;&nbsp;&nbsp;&nbsp;(b) The rate shown is the seven-day current annualized yield at December 31, 2025.

&nbsp;&nbsp;&nbsp;&nbsp;(c) Under the Investment Company Act of 1940, an affiliated company is one in which the Fund owns 5% or more of the company's outstanding voting securities, or a company which is under common ownership or control with the Fund. The value of the holdings and transactions in these affiliated companies during the year ended December 31, 2025 are as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning** <br>**of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br>**unrealized** <br>**appreciation** <br>**(depreciation)($)**<br>| **End of** <br>**period($)**<br>| **Realized gain** <br>**(loss)($)**<br>| **Dividends($)** | **End of** <br>**period shares**<br>|
| Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% |
|  | 2828723 | &nbsp;&nbsp; 37517856 | &nbsp;&nbsp; (37913626)<br>| &nbsp;&nbsp; (169)<br>| &nbsp;&nbsp; 2432784 | &nbsp;&nbsp; 534 | &nbsp;&nbsp; 96429 | &nbsp;&nbsp; 2433514 |

---

**Fair value measurements** 

The Fund categorizes its fair value measurements according to a three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by prioritizing that the most observable input be used when available. Observable inputs are those that market participants would use in pricing an investment based on market data obtained from sources independent of the reporting entity. Unobservable inputs are those that reflect the Fund's assumptions about the information market participants would use in pricing an investment. An investment's level within the fair value hierarchy is based on the lowest level of any input that is deemed significant to the asset's or liability's fair value measurement. The input levels are not necessarily an indication of the risk or liquidity associated with investments at that level. For example, certain U.S. government securities are generally high quality and liquid, however, they are reflected as Level 2 because the inputs used to determine fair value may not always be quoted prices in an active market.

Fair value inputs are summarized in the three broad levels listed below:

■

Level 1 — Valuations based on quoted prices for investments in active markets that the Fund has the ability to access at the measurement date. Valuation adjustments are not applied to Level 1 investments.

■

Level 2 — Valuations based on other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.).

■

Level 3 — Valuations based on significant unobservable inputs (including the Fund's own assumptions and judgment in determining the fair value of investments).

Inputs that are used in determining fair value of an investment may include price information, credit data, volatility statistics, and other factors. These inputs can be either observable or unobservable. The availability of observable inputs can vary between investments, and is affected by various factors such as the type of investment, and the volume and level of activity for that investment or similar investments in the marketplace. The inputs will be considered by the Investment Manager, along with any other relevant factors in the calculation of an investment's fair value. The Fund uses prices and inputs that are current as of the measurement date, which may include periods of market dislocations. During these periods, the availability of prices and inputs may be reduced for many investments. This condition could cause an investment to be reclassified between the various levels within the hierarchy.

Values of foreign equity securities actively traded in markets where there is a significant delay in the local close relative to the New York Stock Exchange may include an adjustment to reflect the impact of market movements following the close of local trading, as described in Note 2 to the financial statements – Security valuation. When such adjustments have been made, the foreign equity securities are classified as Level 2.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn International Select<sup>SM</sup>, December 31, 2025

**Fair value measurements (continued)**

Investments falling into the Level 3 category, if any, are primarily supported by quoted prices from brokers and dealers participating in the market for those investments. However, these may be classified as Level 3 investments due to lack of market transparency and corroboration to support these quoted prices. Additionally, valuation models may be used as the pricing source for any remaining investments classified as Level 3. These models may rely on one or more significant unobservable inputs and/or significant assumptions by the Investment Manager. Inputs used in valuations may include, but are not limited to, financial statement analysis, capital account balances, discount rates and estimated cash flows, and comparable company data.

The Fund's Board of Trustees (the Board) has designated the Investment Manager, through its Valuation Committee (the Committee), as valuation designee, responsible for determining the fair value of the assets of the Fund for which market quotations are not readily available using valuation procedures approved by the Board. The Committee consists of voting and non-voting members from various groups within the Investment Manager's organization, including operations and accounting, trading and investments, compliance, risk management and legal.

The Committee meets at least monthly to review and approve valuation matters, which may include a description of specific valuation determinations, data regarding pricing information received from approved pricing vendors and brokers and the results of Board-approved valuation policies and procedures (the Policies). The Policies address, among other things, instances when market quotations are or are not readily available, including recommendations of third party pricing vendors and a determination of appropriate pricing methodologies; events that require specific valuation determinations and assessment of fair value techniques; securities with a potential for stale pricing, including those that are illiquid, restricted, or in default; and the effectiveness of third party pricing vendors, including periodic reviews of vendors. The Committee meets more frequently, as needed, to discuss additional valuation matters, which may include the need to review back-testing results, review time-sensitive information or approve related valuation actions. Representatives of Columbia Management Investment Advisers, LLC report to the Board at each of its regularly scheduled meetings to discuss valuation matters and actions during the period, similar to those described earlier.

The following table is a summary of the inputs used to value the Fund's investments at December 31, 2025:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| **Investments in Securities** |  |  |  |  |
| Common Stocks |  |  |  |  |
| Australia |  | &nbsp;&nbsp;&nbsp;&nbsp; 2206112 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 2206112 |
| Canada | 1121625 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1121625 |
| Denmark |  | &nbsp;&nbsp;&nbsp;&nbsp; 3001266 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 3001266 |
| Finland |  | &nbsp;&nbsp;&nbsp;&nbsp; 1932553 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1932553 |
| France |  | &nbsp;&nbsp;&nbsp;&nbsp; 36196795 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 36196795 |
| Germany |  | &nbsp;&nbsp;&nbsp;&nbsp; 15198001 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 15198001 |
| Ireland |  | &nbsp;&nbsp;&nbsp;&nbsp; 5135240 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 5135240 |
| Italy |  | &nbsp;&nbsp;&nbsp;&nbsp; 3665285 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 3665285 |
| Japan | 2235184 | &nbsp;&nbsp;&nbsp;&nbsp; 53602646 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 55837830 |
| Netherlands |  | &nbsp;&nbsp;&nbsp;&nbsp; 7188137 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 7188137 |
| New Zealand |  | &nbsp;&nbsp;&nbsp;&nbsp; 1948667 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1948667 |
| Spain |  | &nbsp;&nbsp;&nbsp;&nbsp; 5514779 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 5514779 |
| Switzerland |  | &nbsp;&nbsp;&nbsp;&nbsp; 11474888 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 11474888 |
| United Kingdom |  | &nbsp;&nbsp;&nbsp;&nbsp; 43184239 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 43184239 |
| United States |  | &nbsp;&nbsp;&nbsp;&nbsp; 4529332 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4529332 |
| Total Common Stocks | 3356809 | &nbsp;&nbsp;&nbsp;&nbsp; 194777940 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 198134749 |
| Money Market Funds | 2432784 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 2432784 |
| Total Investments in Securities | 5789593 | &nbsp;&nbsp;&nbsp;&nbsp; 194777940 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 200567533 |

---

See the Portfolio of Investments for all investment classifications not indicated in the table.

The Fund's assets assigned to the Level 2 input category are generally valued using the market approach, in which a security's value is determined through reference to prices and information from market transactions for similar or identical assets. These assets include certain foreign securities for which a third party statistical pricing service may be employed for purposes of fair market valuation. The model utilized by such third party statistical pricing service takes into account a security's correlation to available market data including relevant general and sector indices, currency fluctuations, depositary receipts, and futures, as applicable.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments

Columbia Thermostat Fund<sup>SM</sup>, December 31, 2025

(Percentages represent value of investments compared to net assets)

**Investments in securities**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Equity Funds 24.1%** | **Equity Funds 24.1%** | **Equity Funds 24.1%** |
|  | **Shares** | **Value ($)** |
| **U.S. Large Cap 24.1%** | **U.S. Large Cap 24.1%** | **U.S. Large Cap 24.1%** |
| Columbia Contrarian Core Fund, Institutional 3 <br> Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 2443732 | &nbsp;&nbsp; 97651520 |
| Columbia Cornerstone Growth Fund, Institutional <br> 3 Class<sup>(a),(b)</sup> <br>| &nbsp;&nbsp; 473526 | &nbsp;&nbsp; 39255313 |
| Columbia Large Cap Enhanced Core Fund, <br> Institutional 3 Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 3429273 | &nbsp;&nbsp; 97597120 |
| Columbia Large Cap Index Fund, Institutional 3 <br> Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 1500185 | &nbsp;&nbsp; 77979626 |
| **Total** | **Total** | &nbsp;&nbsp; **312483579** |
| Total Equity Funds <br>(Cost $261,388,479) | Total Equity Funds <br>(Cost $261,388,479) | &nbsp;&nbsp; **312483579** |
| **Exchange-Traded Equity Funds 6.0%** | **Exchange-Traded Equity Funds 6.0%** | **Exchange-Traded Equity Funds 6.0%** |
| **U.S. Large Cap 6.0%** | **U.S. Large Cap 6.0%** | **U.S. Large Cap 6.0%** |
| Columbia Research Enhanced Core ETF<sup>(a)</sup> <br>| &nbsp;&nbsp; 1899723 | &nbsp;&nbsp; 77584688 |
| Total Exchange-Traded Equity Funds <br>(Cost $59,698,521) | Total Exchange-Traded Equity Funds <br>(Cost $59,698,521) | &nbsp;&nbsp; **77584688** |
| **Exchange-Traded Fixed Income Funds 6.9%** | **Exchange-Traded Fixed Income Funds 6.9%** | **Exchange-Traded Fixed Income Funds 6.9%** |
| **Multisector 6.9%** | **Multisector 6.9%** | **Multisector 6.9%** |
| Columbia Diversified Fixed Income Allocation <br> ETF<sup>(a)</sup> <br>| &nbsp;&nbsp; 4887459 | &nbsp;&nbsp; 89709310 |
| Total Exchange-Traded Fixed Income Funds <br>(Cost $88,825,465) | Total Exchange-Traded Fixed Income Funds <br>(Cost $88,825,465) | &nbsp;&nbsp; **89709310** |

---

---

| | | |
|:---|:---|:---|
| **Fixed Income Funds 62.5%** | **Fixed Income Funds 62.5%** | **Fixed Income Funds 62.5%** |
|  | **Shares** | **Value ($)** |
| **High Yield 7.0%** | **High Yield 7.0%** | **High Yield 7.0%** |
| Columbia High Yield Bond Fund, Institutional 3 <br> Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 8108133 | &nbsp;&nbsp; 90648928 |
| **Investment Grade 55.5%** | **Investment Grade 55.5%** | **Investment Grade 55.5%** |
| Columbia Quality Income Fund, Institutional 3 <br> Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 7385139 | &nbsp;&nbsp; 134926489 |
| Columbia Select Corporate Income Fund, <br> Institutional 3 Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 19465314 | &nbsp;&nbsp; 180248809 |
| Columbia Total Return Bond Fund, Institutional 3 <br> Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 7285995 | &nbsp;&nbsp; 225428660 |
| Columbia U.S. Treasury Index Fund, Institutional <br> 3 Class<sup>(a)</sup> <br>| &nbsp;&nbsp; 17921783 | &nbsp;&nbsp; 179934702 |
| **Total** | **Total** | &nbsp;&nbsp; **720538660** |
| Total Fixed Income Funds <br>(Cost $787,089,911) | Total Fixed Income Funds <br>(Cost $787,089,911) | &nbsp;&nbsp; **811187588** |
| **Money Market Funds 0.5%** | **Money Market Funds 0.5%** | **Money Market Funds 0.5%** |
| Columbia Short-Term Cash Fund, 3.825%<sup>(a),(c)</sup> <br>| &nbsp;&nbsp; 6222128 | &nbsp;&nbsp; 6220261 |
| Total Money Market Funds <br>(Cost $6,219,946) | Total Money Market Funds <br>(Cost $6,219,946) | &nbsp;&nbsp; **6220261** |
| **Total Investments in Securities** <br>**(Cost: $1,203,222,322)** | **Total Investments in Securities** <br>**(Cost: $1,203,222,322)** | &nbsp;&nbsp; **1297185426** |
| **Other Assets & Liabilities, Net** |  | &nbsp;&nbsp; **(538827)**<br>|
| **Net Assets** | **Net Assets** | &nbsp;&nbsp; **1296646599** |

---

**Notes to Portfolio of Investments** 

&nbsp;&nbsp;&nbsp;&nbsp;(a) Under the Investment Company Act of 1940, an affiliated company is one in which the Fund owns 5% or more of the company's outstanding voting securities, or a company which is under common ownership or control with the Fund. The value of the holdings and transactions in these affiliated companies during the year ended December 31, 2025 are as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning** <br>**of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br>**unrealized** <br>**appreciation** <br>**(depreciation)($)**<br>| **End of** <br>**period($)**<br>| **Capital gain** <br>**distributions($)**<br>| **Realized gain** <br>**(loss)($)**<br>| **Dividends —** <br>**affiliated** <br>**issuers ($)**<br>| **End of** <br>**period shares**<br>|
| Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  | Columbia Contrarian Core Fund, Institutional 3 Class  |
|  | 74265906 | 121321084 | (105751581)<br>| 7816111 | 97651520 | 5212499 | 14978334 | 340619 | 2443732 |
| Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  | Columbia Cornerstone Growth Fund, Institutional 3 Class  |
|  | 29688679 | 51305193 | (44446605)<br>| 2708046 | 39255313 | 2616994 | 7100098 |  | 473526 |
| Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  | Columbia Diversified Fixed Income Allocation ETF  |
|  | 89144643 | 44441566 | (48689879)<br>| 4812980 | 89709310 |  | (1427212)<br>| 4006707 | 4887459 |
| Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  | Columbia High Yield Bond Fund, Institutional 3 Class  |
|  | 90169866 | 47176365 | (48277198)<br>| 1579895 | 90648928 |  | (519567)<br>| 5018100 | 8108133 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Thermostat Fund<sup>SM</sup>, December 31, 2025

**Notes to Portfolio of Investments (continued)**

---

| | | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning**<br> **of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br> **unrealized** <br> **appreciation** <br> **(depreciation)($)**<br>| **End of** <br> **period($)**<br>| **Capital gain**<br> **distributions($)**<br>| **Realized gain**<br> **(loss)($)**<br>| **Dividends —**<br> **affiliated**<br> **issuers ($)**<br>| **End of**<br> **period shares**<br>|
| Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  | Columbia Large Cap Enhanced Core Fund, Institutional 3 Class  |
|  | 74525468 | 124401326 | (107596484)<br>| 6266810 | 97597120 | 10358028 | 9548287 | 955845 | 3429273 |
| Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  | Columbia Large Cap Index Fund, Institutional 3 Class  |
|  | 59756842 | 110422775 | (87987310)<br>| (4212681)<br>| 77979626 | 18833477 | 6676863 | 811133 | 1500185 |
| Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  | Columbia Quality Income Fund, Institutional 3 Class  |
|  | 134970124 | 72489488 | (86529548)<br>| 13996425 | 134926489 |  | (7538701)<br>| 5507976 | 7385139 |
| Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  | Columbia Research Enhanced Core ETF  |
|  | 29495409 | 110971409 | (74370616)<br>| 11488486 | 77584688 | 207480 | 9730195 | 515768 | 1899723 |
| Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  | Columbia Select Corporate Income Fund, Institutional 3 Class  |
|  | 180071090 | 95141102 | (102462671)<br>| 7499288 | 180248809 |  | (3477236)<br>| 7682339 | 19465314 |
| Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  | Columbia Short-Term Cash Fund, 3.825%  |
|  | 3388538 | 124964336 | (122132927)<br>| 314 | 6220261 |  | (259)<br>| 215304 | 6222128 |
| Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  | Columbia Small Cap Index Fund, Institutional 3 Class  |
|  | 28668806 | 41403621 | (70048921)<br>| (23506)<br>|  |  | (2602376)<br>|  |  |
| Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  | Columbia Total Return Bond Fund, Institutional 3 Class  |
|  | 225118342 | 121430257 | (130042066)<br>| 8922127 | 225428660 |  | (802142)<br>| 10240945 | 7285995 |
| Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  | Columbia U.S. Treasury Index Fund, Institutional 3 Class  |
|  | 179923815 | 97626677 | (104225739)<br>| 6609949 | 179934702 |  | (2005764)<br>| 5909799 | 17921783 |
| Total | 1199187528 |  |  | 67464244 | 1297185426 | 37228478 | 29660520 | 41204535 |  |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(b) Non-income producing investment.

&nbsp;&nbsp;&nbsp;&nbsp;(c) The rate shown is the seven-day current annualized yield at December 31, 2025.

**Fair value measurements** 

The Fund categorizes its fair value measurements according to a three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by prioritizing that the most observable input be used when available. Observable inputs are those that market participants would use in pricing an investment based on market data obtained from sources independent of the reporting entity. Unobservable inputs are those that reflect the Fund's assumptions about the information market participants would use in pricing an investment. An investment's level within the fair value hierarchy is based on the lowest level of any input that is deemed significant to the asset's or liability's fair value measurement. The input levels are not necessarily an indication of the risk or liquidity associated with investments at that level. For example, certain U.S. government securities are generally high quality and liquid, however, they are reflected as Level 2 because the inputs used to determine fair value may not always be quoted prices in an active market.

Fair value inputs are summarized in the three broad levels listed below:

■

Level 1 — Valuations based on quoted prices for investments in active markets that the Fund has the ability to access at the measurement date. Valuation adjustments are not applied to Level 1 investments.

■

Level 2 — Valuations based on other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.).

■

Level 3 — Valuations based on significant unobservable inputs (including the Fund's own assumptions and judgment in determining the fair value of investments).

Inputs that are used in determining fair value of an investment may include price information, credit data, volatility statistics, and other factors. These inputs can be either observable or unobservable. The availability of observable inputs can vary between investments, and is affected by various factors such as the type of investment, and the volume and level of activity for that investment or similar investments in the marketplace. The inputs will be considered by the Investment Manager, along with any other relevant factors in the calculation of an investment's fair value. The Fund uses prices and inputs that are current as of the measurement date, which may include periods of market dislocations. During these periods, the availability of prices and inputs may be reduced for many investments. This condition could cause an investment to be reclassified between the various levels within the hierarchy.

Investments falling into the Level 3 category, if any, are primarily supported by quoted prices from brokers and dealers participating in the market for those investments. However, these may be classified as Level 3 investments due to lack of market transparency and corroboration to support these quoted prices. Additionally, valuation models may be used as the pricing source for any remaining investments classified as Level 3. These models may rely on one or more significant unobservable inputs and/or significant assumptions by the Investment Manager. Inputs used in valuations may include, but are not limited to, financial statement analysis, capital account balances, discount rates and estimated cash flows, and comparable company data.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Thermostat Fund<sup>SM</sup>, December 31, 2025

**Fair value measurements (continued)**

The Fund's Board of Trustees (the Board) has designated the Investment Manager, through its Valuation Committee (the Committee), as valuation designee, responsible for determining the fair value of the assets of the Fund for which market quotations are not readily available using valuation procedures approved by the Board. The Committee consists of voting and non-voting members from various groups within the Investment Manager's organization, including operations and accounting, trading and investments, compliance, risk management and legal.

The Committee meets at least monthly to review and approve valuation matters, which may include a description of specific valuation determinations, data regarding pricing information received from approved pricing vendors and brokers and the results of Board-approved valuation policies and procedures (the Policies). The Policies address, among other things, instances when market quotations are or are not readily available, including recommendations of third party pricing vendors and a determination of appropriate pricing methodologies; events that require specific valuation determinations and assessment of fair value techniques; securities with a potential for stale pricing, including those that are illiquid, restricted, or in default; and the effectiveness of third party pricing vendors, including periodic reviews of vendors. The Committee meets more frequently, as needed, to discuss additional valuation matters, which may include the need to review back-testing results, review time-sensitive information or approve related valuation actions. Representatives of Columbia Management Investment Advisers, LLC report to the Board at each of its regularly scheduled meetings to discuss valuation matters and actions during the period, similar to those described earlier.

The following table is a summary of the inputs used to value the Fund's investments at December 31, 2025:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| **Investments in Securities** |  |  |  |  |
| Equity Funds | 312483579 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 312483579 |
| Exchange-Traded Equity Funds | 77584688 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 77584688 |
| Exchange-Traded Fixed Income Funds | 89709310 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 89709310 |
| Fixed Income Funds | 811187588 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 811187588 |
| Money Market Funds | 6220261 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 6220261 |
| Total Investments in Securities | 1297185426 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1297185426 |

---

See the Portfolio of Investments for all investment classifications not indicated in the table.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments

Columbia Acorn European Fund<sup>SM</sup>, December 31, 2025

(Percentages represent value of investments compared to net assets)

**Investments in securities**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Common Stocks 97.7%** | **Common Stocks 97.7%** | **Common Stocks 97.7%** |
| **Issuer** | **Shares** | **Value ($)** |
| **Austria 4.9%** | **Austria 4.9%** | **Austria 4.9%** |
| BAWAG Group AG | &nbsp;&nbsp; 2951 | &nbsp;&nbsp; 444462 |
| DO & CO AG | &nbsp;&nbsp; 3247 | &nbsp;&nbsp; 789886 |
| Wienerberger AG | &nbsp;&nbsp; 15445 | &nbsp;&nbsp; 551129 |
| **Total** | **Total** | &nbsp;&nbsp; **1785477** |
| **Belgium 1.6%** | **Belgium 1.6%** | **Belgium 1.6%** |
| Elia Group SA/NV | &nbsp;&nbsp; 2933 | &nbsp;&nbsp; 377427 |
| Warehouses De Pauw CVA | &nbsp;&nbsp; 7705 | &nbsp;&nbsp; 199817 |
| **Total** | **Total** | &nbsp;&nbsp; **577244** |
| **Burkina Faso 0.6%** | **Burkina Faso 0.6%** | **Burkina Faso 0.6%** |
| Endeavour Mining PLC | &nbsp;&nbsp; 3873 | &nbsp;&nbsp; 202354 |
| **Denmark 1.2%** | **Denmark 1.2%** | **Denmark 1.2%** |
| NKT A/S<sup>(a)</sup> <br>| &nbsp;&nbsp; 3614 | &nbsp;&nbsp; 451305 |
| **Finland 2.1%** | **Finland 2.1%** | **Finland 2.1%** |
| Konecranes OYJ | &nbsp;&nbsp; 5515 | &nbsp;&nbsp; 603923 |
| Valmet OYJ | &nbsp;&nbsp; 5555 | &nbsp;&nbsp; 183580 |
| **Total** | **Total** | &nbsp;&nbsp; **787503** |
| **France 13.3%** | **France 13.3%** | **France 13.3%** |
| Elis SA | &nbsp;&nbsp; 38919 | &nbsp;&nbsp; 1104345 |
| Exosens SAS | &nbsp;&nbsp; 3275 | &nbsp;&nbsp; 186155 |
| Gaztransport Et Technigaz SA | &nbsp;&nbsp; 2049 | &nbsp;&nbsp; 375964 |
| Nexans SA | &nbsp;&nbsp; 6458 | &nbsp;&nbsp; 949327 |
| SCOR SE | &nbsp;&nbsp; 11648 | &nbsp;&nbsp; 392103 |
| SPIE SA | &nbsp;&nbsp; 13963 | &nbsp;&nbsp; 804987 |
| Technip Energies NV | &nbsp;&nbsp; 16269 | &nbsp;&nbsp; 619554 |
| Virbac SA | &nbsp;&nbsp; 1046 | &nbsp;&nbsp; 438591 |
| **Total** | **Total** | &nbsp;&nbsp; **4871026** |
| **Germany 9.4%** | **Germany 9.4%** | **Germany 9.4%** |
| AlzChem Group AG | &nbsp;&nbsp; 1405 | &nbsp;&nbsp; 253790 |
| Bilfinger SE | &nbsp;&nbsp; 5705 | &nbsp;&nbsp; 713808 |
| CTS Eventim AG & Co. KGaA | &nbsp;&nbsp; 6941 | &nbsp;&nbsp; 635395 |
| flatexDEGIRO AG | &nbsp;&nbsp; 22896 | &nbsp;&nbsp; 980909 |
| IONOS Group SE<sup>(a)</sup> <br>| &nbsp;&nbsp; 9898 | &nbsp;&nbsp; 308683 |
| PVA TePla AG<sup>(a)</sup> <br>| &nbsp;&nbsp; 1271 | &nbsp;&nbsp; 33756 |
| Renk Group AG | &nbsp;&nbsp; 3499 | &nbsp;&nbsp; 218062 |
| Schott Pharma AG & Co., KGaA | &nbsp;&nbsp; 7025 | &nbsp;&nbsp; 123434 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| SUSS MicroTec SE | &nbsp;&nbsp; 4179 | &nbsp;&nbsp; 189038 |
| **Total** | **Total** | &nbsp;&nbsp; **3456875** |
| **Greece 3.8%** | **Greece 3.8%** | **Greece 3.8%** |
| Alpha Bank SA | &nbsp;&nbsp; 136278 | &nbsp;&nbsp; 572787 |
| JUMBO SA | &nbsp;&nbsp; 5623 | &nbsp;&nbsp; 184367 |
| Piraeus Bank SA<sup>(a)</sup> <br>| &nbsp;&nbsp; 80887 | &nbsp;&nbsp; 645827 |
| **Total** | **Total** | &nbsp;&nbsp; **1402981** |
| **Ireland 5.4%** | **Ireland 5.4%** | **Ireland 5.4%** |
| Cairn Homes PLC | &nbsp;&nbsp; 251218 | &nbsp;&nbsp; 611163 |
| Glanbia PLC | &nbsp;&nbsp; 26061 | &nbsp;&nbsp; 446847 |
| Irish Continental Group PLC | &nbsp;&nbsp; 59876 | &nbsp;&nbsp; 423605 |
| Permanent TSB Group Holdings PLC<sup>(a)</sup> <br>| &nbsp;&nbsp; 48061 | &nbsp;&nbsp; 162101 |
| Uniphar PLC | &nbsp;&nbsp; 83567 | &nbsp;&nbsp; 343311 |
| **Total** | **Total** | &nbsp;&nbsp; **1987027** |
| **Italy 6.4%** | **Italy 6.4%** | **Italy 6.4%** |
| Buzzi SpA | &nbsp;&nbsp; 9542 | &nbsp;&nbsp; 576825 |
| Carel Industries SpA | &nbsp;&nbsp; 7898 | &nbsp;&nbsp; 226924 |
| De' Longhi SpA | &nbsp;&nbsp; 11089 | &nbsp;&nbsp; 472059 |
| Hera | &nbsp;&nbsp; 131848 | &nbsp;&nbsp; 621713 |
| Intercos SpA | &nbsp;&nbsp; 15285 | &nbsp;&nbsp; 198670 |
| Reply SpA | &nbsp;&nbsp; 1866 | &nbsp;&nbsp; 249847 |
| **Total** | **Total** | &nbsp;&nbsp; **2346038** |
| **Jersey 0.5%** | **Jersey 0.5%** | **Jersey 0.5%** |
| JTC PLC | &nbsp;&nbsp; 10437 | &nbsp;&nbsp; 180640 |
| **Luxembourg 0.5%** | **Luxembourg 0.5%** | **Luxembourg 0.5%** |
| Tonies SE, Class A<sup>(a)</sup> <br>| &nbsp;&nbsp; 16151 | &nbsp;&nbsp; 196895 |
| **Netherlands 3.1%** | **Netherlands 3.1%** | **Netherlands 3.1%** |
| CTP NV<sup>(b)</sup> <br>| &nbsp;&nbsp; 35710 | &nbsp;&nbsp; 748281 |
| Van Lanschot Kempen NV | &nbsp;&nbsp; 6287 | &nbsp;&nbsp; 389776 |
| **Total** | **Total** | &nbsp;&nbsp; **1138057** |
| **Norway 3.1%** | **Norway 3.1%** | **Norway 3.1%** |
| SalMar ASA | &nbsp;&nbsp; 6941 | &nbsp;&nbsp; 424221 |
| Storebrand ASA | &nbsp;&nbsp; 40657 | &nbsp;&nbsp; 694859 |
| **Total** | **Total** | &nbsp;&nbsp; **1119080** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn European Fund<sup>SM</sup>, December 31, 2025

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| **Spain 3.5%** | **Spain 3.5%** | **Spain 3.5%** |
| Fluidra SA | &nbsp;&nbsp; 18855 | &nbsp;&nbsp; 510821 |
| Merlin Properties Socimi SA | &nbsp;&nbsp; 14446 | &nbsp;&nbsp; 210312 |
| Vidrala SA | &nbsp;&nbsp; 3532 | &nbsp;&nbsp; 373101 |
| Viscofan SA | &nbsp;&nbsp; 3128 | &nbsp;&nbsp; 196118 |
| **Total** | **Total** | &nbsp;&nbsp; **1290352** |
| **Sweden 3.1%** | **Sweden 3.1%** | **Sweden 3.1%** |
| Avanza Bank Holding AB | &nbsp;&nbsp; 9801 | &nbsp;&nbsp; 372209 |
| Hexpol AB | &nbsp;&nbsp; 40001 | &nbsp;&nbsp; 380459 |
| Nordnet AB | &nbsp;&nbsp; 13621 | &nbsp;&nbsp; 397321 |
| **Total** | **Total** | &nbsp;&nbsp; **1149989** |
| **Switzerland 4.6%** | **Switzerland 4.6%** | **Switzerland 4.6%** |
| Accelleron Industries AG | &nbsp;&nbsp; 2213 | &nbsp;&nbsp; 170681 |
| Burckhardt Compression Holding AG | &nbsp;&nbsp; 395 | &nbsp;&nbsp; 270638 |
| Comet Holding AG, Registered Shares | &nbsp;&nbsp; 735 | &nbsp;&nbsp; 205567 |
| Galenica AG | &nbsp;&nbsp; 2599 | &nbsp;&nbsp; 320569 |
| Huber + Suhner AG, Registered Shares | &nbsp;&nbsp; 1111 | &nbsp;&nbsp; 201490 |
| Kardex Holding AG | &nbsp;&nbsp; 942 | &nbsp;&nbsp; 326241 |
| R&S Group Holding AG | &nbsp;&nbsp; 8852 | &nbsp;&nbsp; 175919 |
| **Total** | **Total** | &nbsp;&nbsp; **1671105** |
| **United Kingdom 30.1%** | **United Kingdom 30.1%** | **United Kingdom 30.1%** |
| Allfunds Group PLC | &nbsp;&nbsp; 36544 | &nbsp;&nbsp; 345089 |
| Avon Technologies PLC | &nbsp;&nbsp; 8072 | &nbsp;&nbsp; 197375 |
| Babcock International Group PLC | &nbsp;&nbsp; 23899 | &nbsp;&nbsp; 398272 |
| Beazley PLC | &nbsp;&nbsp; 44507 | &nbsp;&nbsp; 497704 |
| Breedon Group PLC | &nbsp;&nbsp; 63048 | &nbsp;&nbsp; 279772 |
| Bridgepoint Group Ltd., Registered Shares<sup>(b)</sup> <br>| &nbsp;&nbsp; 84229 | &nbsp;&nbsp; 320863 |
| Capital & Counties Properties PLC | &nbsp;&nbsp; 292802 | &nbsp;&nbsp; 571168 |
| Chemring Group PLC | &nbsp;&nbsp; 85614 | &nbsp;&nbsp; 543175 |
| Clarkson PLC | &nbsp;&nbsp; 4702 | &nbsp;&nbsp; 241245 |

---

---

| | | |
|:---|:---|:---|
| **Common Stocks (continued)** | **Common Stocks (continued)** | **Common Stocks (continued)** |
| **Issuer** | **Shares** | **Value ($)** |
| ConvaTec Group PLC | &nbsp;&nbsp; 116270 | &nbsp;&nbsp; 379612 |
| CVS Group PLC | &nbsp;&nbsp; 44407 | &nbsp;&nbsp; 768593 |
| discoverIE Group plc | &nbsp;&nbsp; 27711 | &nbsp;&nbsp; 224118 |
| Genus PLC | &nbsp;&nbsp; 15587 | &nbsp;&nbsp; 543984 |
| GlobalData PLC | &nbsp;&nbsp; 85156 | &nbsp;&nbsp; 126839 |
| Howden Joinery Group PLC | &nbsp;&nbsp; 16753 | &nbsp;&nbsp; 187492 |
| ICG PLC | &nbsp;&nbsp; 14048 | &nbsp;&nbsp; 387390 |
| IG Group Holdings PLC | &nbsp;&nbsp; 27224 | &nbsp;&nbsp; 481963 |
| IMI PLC | &nbsp;&nbsp; 13001 | &nbsp;&nbsp; 433673 |
| LondonMetric Property PLC | &nbsp;&nbsp; 270050 | &nbsp;&nbsp; 688479 |
| Moonpig Group PLC | &nbsp;&nbsp; 190740 | &nbsp;&nbsp; 521929 |
| Quilter PLC<sup>(b)</sup> <br>| &nbsp;&nbsp; 283799 | &nbsp;&nbsp; 700061 |
| Rotork PLC | &nbsp;&nbsp; 85467 | &nbsp;&nbsp; 374139 |
| Safestore Holdings PLC | &nbsp;&nbsp; 73231 | &nbsp;&nbsp; 726518 |
| Shawbrook Group PLC<sup>(a),(b)</sup> <br>| &nbsp;&nbsp; 91314 | &nbsp;&nbsp; 598201 |
| SigmaRoc PLC<sup>(a)</sup> <br>| &nbsp;&nbsp; 293617 | &nbsp;&nbsp; 502400 |
| **Total** | **Total** | &nbsp;&nbsp; **11040054** |
| **United States 0.5%** | **United States 0.5%** | **United States 0.5%** |
| Boku, Inc.<sup>(a)</sup> <br>| &nbsp;&nbsp; 60552 | &nbsp;&nbsp; 171404 |
| Total Common Stocks <br>(Cost $30,639,293) | Total Common Stocks <br>(Cost $30,639,293) | &nbsp;&nbsp; **35825406** |
| **Money Market Funds 0.9%** | **Money Market Funds 0.9%** | **Money Market Funds 0.9%** |
|  | **Shares** | **Value ($)** |
| Columbia Short-Term Cash Fund, 3.825%<sup>(c),(d)</sup> <br>| &nbsp;&nbsp; 326252 | &nbsp;&nbsp; 326154 |
| Total Money Market Funds <br>(Cost $326,153) | Total Money Market Funds <br>(Cost $326,153) | &nbsp;&nbsp; **326154** |
| **Total Investments in Securities** <br>**(Cost $30,965,446)** | **Total Investments in Securities** <br>**(Cost $30,965,446)** | &nbsp;&nbsp; **36151560** |
| **Other Assets & Liabilities, Net** |  | &nbsp;&nbsp; **520814** |
| **Net Assets** | **Net Assets** | &nbsp;&nbsp; **$36672374** |

---

**Notes to Portfolio of Investments** 

&nbsp;&nbsp;&nbsp;&nbsp;(a) Non-income producing investment.

&nbsp;&nbsp;&nbsp;&nbsp;(b) Represents privately placed and other securities and instruments exempt from Securities and Exchange Commission registration (collectively, private placements), such as Section 4(a)(2) and Rule 144A eligible securities, which are often sold only to qualified institutional buyers. At December 31, 2025, the total value of these securities amounted to $2,367,406, which represents 6.46% of total net assets.

&nbsp;&nbsp;&nbsp;&nbsp;(c) The rate shown is the seven-day current annualized yield at December 31, 2025.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn European Fund<sup>SM</sup>, December 31, 2025

**Notes to Portfolio of Investments (continued)**

&nbsp;&nbsp;&nbsp;&nbsp;(d) Under the Investment Company Act of 1940, an affiliated company is one in which the Fund owns 5% or more of the company's outstanding voting securities, or a company which is under common ownership or control with the Fund. The value of the holdings and transactions in these affiliated companies during the year ended December 31, 2025 are as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Affiliated issuers** | **Beginning** <br>**of period($)**<br>| **Purchases($)** | **Sales($)** | **Net change in** <br>**unrealized** <br>**appreciation** <br>**(depreciation)($)**<br>| **End of** <br>**period($)**<br>| **Realized gain** <br>**(loss)($)**<br>| **Dividends($)** | **End of** <br>**period shares**<br>|
| Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% | Columbia Short-Term Cash Fund, 3.825% |
|  | 361715 | &nbsp;&nbsp; 20494900 | &nbsp;&nbsp; (20530462)<br>| &nbsp;&nbsp; 1 | &nbsp;&nbsp; 326154 | &nbsp;&nbsp; (185)<br>| &nbsp;&nbsp; 18031 | &nbsp;&nbsp; 326252 |

---

**Fair value measurements** 

The Fund categorizes its fair value measurements according to a three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by prioritizing that the most observable input be used when available. Observable inputs are those that market participants would use in pricing an investment based on market data obtained from sources independent of the reporting entity. Unobservable inputs are those that reflect the Fund's assumptions about the information market participants would use in pricing an investment. An investment's level within the fair value hierarchy is based on the lowest level of any input that is deemed significant to the asset's or liability's fair value measurement. The input levels are not necessarily an indication of the risk or liquidity associated with investments at that level. For example, certain U.S. government securities are generally high quality and liquid, however, they are reflected as Level 2 because the inputs used to determine fair value may not always be quoted prices in an active market.

Fair value inputs are summarized in the three broad levels listed below:

■

Level 1 — Valuations based on quoted prices for investments in active markets that the Fund has the ability to access at the measurement date. Valuation adjustments are not applied to Level 1 investments.

■

Level 2 — Valuations based on other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.).

■

Level 3 — Valuations based on significant unobservable inputs (including the Fund's own assumptions and judgment in determining the fair value of investments).

Inputs that are used in determining fair value of an investment may include price information, credit data, volatility statistics, and other factors. These inputs can be either observable or unobservable. The availability of observable inputs can vary between investments, and is affected by various factors such as the type of investment, and the volume and level of activity for that investment or similar investments in the marketplace. The inputs will be considered by the Investment Manager, along with any other relevant factors in the calculation of an investment's fair value. The Fund uses prices and inputs that are current as of the measurement date, which may include periods of market dislocations. During these periods, the availability of prices and inputs may be reduced for many investments. This condition could cause an investment to be reclassified between the various levels within the hierarchy.

Values of foreign equity securities actively traded in markets where there is a significant delay in the local close relative to the New York Stock Exchange may include an adjustment to reflect the impact of market movements following the close of local trading, as described in Note 2 to the financial statements – Security valuation. When such adjustments have been made, the foreign equity securities are classified as Level 2.

Investments falling into the Level 3 category, if any, are primarily supported by quoted prices from brokers and dealers participating in the market for those investments. However, these may be classified as Level 3 investments due to lack of market transparency and corroboration to support these quoted prices. Additionally, valuation models may be used as the pricing source for any remaining investments classified as Level 3. These models may rely on one or more significant unobservable inputs and/or significant assumptions by the Investment Manager. Inputs used in valuations may include, but are not limited to, financial statement analysis, capital account balances, discount rates and estimated cash flows, and comparable company data.

The Fund's Board of Trustees (the Board) has designated the Investment Manager, through its Valuation Committee (the Committee), as valuation designee, responsible for determining the fair value of the assets of the Fund for which market quotations are not readily available using valuation procedures approved by the Board. The Committee consists of voting and non-voting members from various groups within the Investment Manager's organization, including operations and accounting, trading and investments, compliance, risk management and legal.

The Committee meets at least monthly to review and approve valuation matters, which may include a description of specific valuation determinations, data regarding pricing information received from approved pricing vendors and brokers and the results of Board-approved valuation policies and procedures (the Policies). The Policies address, among other things, instances when market quotations are or are not readily available, including recommendations of third party pricing vendors and a determination of appropriate pricing methodologies; events that require specific valuation determinations and assessment of fair value techniques; securities with a potential for stale pricing, including those that are illiquid, restricted, or in default; and the effectiveness of third party pricing vendors, including periodic reviews of vendors. The Committee meets more frequently, as needed, to discuss additional valuation matters, which may include the need to review back-testing results, review time-sensitive information or approve related valuation actions. Representatives of Columbia Management Investment Advisers, LLC report to the Board at each of its regularly scheduled meetings to discuss valuation matters and actions during the period, similar to those described earlier.

The following table is a summary of the inputs used to value the Fund's investments at December 31, 2025:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| **Investments in Securities** |  |  |  |  |
| Common Stocks |  |  |  |  |
| Austria | 789886 | &nbsp;&nbsp;&nbsp;&nbsp; 995591 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1785477 |
| Belgium |  | &nbsp;&nbsp;&nbsp;&nbsp; 577244 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 577244 |
| Burkina Faso |  | &nbsp;&nbsp;&nbsp;&nbsp; 202354 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 202354 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Portfolio of Investments (continued)

Columbia Acorn European Fund<sup>SM</sup>, December 31, 2025

**Fair value measurements (continued)**

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Level 1 ($)** | **Level 2 ($)** | **Level 3 ($)** | **Total ($)** |
| Denmark |  | &nbsp;&nbsp;&nbsp;&nbsp; 451305 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 451305 |
| Finland |  | &nbsp;&nbsp;&nbsp;&nbsp; 787503 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 787503 |
| France |  | &nbsp;&nbsp;&nbsp;&nbsp; 4871026 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4871026 |
| Germany |  | &nbsp;&nbsp;&nbsp;&nbsp; 3456875 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 3456875 |
| Greece | 830194 | &nbsp;&nbsp;&nbsp;&nbsp; 572787 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1402981 |
| Ireland | 870452 | &nbsp;&nbsp;&nbsp;&nbsp; 1116575 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1987027 |
| Italy | 198670 | &nbsp;&nbsp;&nbsp;&nbsp; 2147368 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 2346038 |
| Jersey | 180640 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 180640 |
| Luxembourg |  | &nbsp;&nbsp;&nbsp;&nbsp; 196895 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 196895 |
| Netherlands |  | &nbsp;&nbsp;&nbsp;&nbsp; 1138057 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1138057 |
| Norway |  | &nbsp;&nbsp;&nbsp;&nbsp; 1119080 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1119080 |
| Spain |  | &nbsp;&nbsp;&nbsp;&nbsp; 1290352 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1290352 |
| Sweden |  | &nbsp;&nbsp;&nbsp;&nbsp; 1149989 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1149989 |
| Switzerland | 320569 | &nbsp;&nbsp;&nbsp;&nbsp; 1350536 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 1671105 |
| United Kingdom | 3374813 | &nbsp;&nbsp;&nbsp;&nbsp; 7665241 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 11040054 |
| United States | 171404 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 171404 |
| Total Common Stocks | 6736628 | &nbsp;&nbsp;&nbsp;&nbsp; 29088778 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 35825406 |
| Money Market Funds | 326154 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 326154 |
| Total Investments in Securities | 7062782 | &nbsp;&nbsp;&nbsp;&nbsp; 29088778 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 36151560 |

---

See the Portfolio of Investments for all investment classifications not indicated in the table.

The Fund's assets assigned to the Level 2 input category are generally valued using the market approach, in which a security's value is determined through reference to prices and information from market transactions for similar or identical assets. These assets include certain foreign securities for which a third party statistical pricing service may be employed for purposes of fair market valuation. The model utilized by such third party statistical pricing service takes into account a security's correlation to available market data including relevant general and sector indices, currency fluctuations, depositary receipts, and futures, as applicable.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Assets and Liabilities

December 31, 2025

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | |
|:---|:---|:---|:---|
|  | **Columbia** <br>**Acorn**<sup>®</sup> <br>**Fund**<br>| **Columbia** <br>**Acorn** <br>**International**<sup>®</sup><br>| **Columbia** <br>**Acorn** <br>**International** <br>**Select**<sup>SM</sup><br>|
| **Assets** |  |  |  |
| Investments in securities, at value |  |  |  |
| Unaffiliated issuers (cost $1,960,851,976, $583,483,523, $158,498,106, respectively) | $2369025065 | &nbsp;&nbsp; $803549171 | &nbsp;&nbsp; $198134749 |
| Affiliated issuers (cost $54,275,361, $4,175,497, $2,432,754, respectively) | 65412555 | &nbsp;&nbsp; 4175673 | &nbsp;&nbsp; 2432784 |
| Foreign currency (cost $20, $5,567, $156, respectively) | 21 | &nbsp;&nbsp; 5556 | &nbsp;&nbsp; 156 |
| Receivable for: |  |  |  |
| Investments sold | 7523066 | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Capital shares sold | 154949 | &nbsp;&nbsp; 43203 | &nbsp;&nbsp; 1118 |
| Dividends | 511270 | &nbsp;&nbsp; 818993 | &nbsp;&nbsp; 240644 |
| Foreign tax reclaims | 3718 | &nbsp;&nbsp; 2112085 | &nbsp;&nbsp; 641231 |
| Expense reimbursement due from Investment Manager | 1043 | &nbsp;&nbsp; 1794 | &nbsp;&nbsp; 2114 |
| Prepaid expenses | 5476 | &nbsp;&nbsp; 3058 | &nbsp;&nbsp; 1935 |
| Deferred compensation of board members | 182 | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Total assets | 2442637345 | &nbsp;&nbsp; 810709533 | &nbsp;&nbsp; 201454731 |
| **Liabilities** |  |  |  |
| Payable for: |  |  |  |
| Capital shares redeemed | 1647260 | &nbsp;&nbsp; 1043783 | &nbsp;&nbsp; 52200 |
| Management services fees | 48772 | &nbsp;&nbsp; 19382 | &nbsp;&nbsp; 4819 |
| Distribution and/or service fees | 3439 | &nbsp;&nbsp; 796 | &nbsp;&nbsp; 805 |
| Transfer agent fees | 197427 | &nbsp;&nbsp; 55278 | &nbsp;&nbsp; 20199 |
| Compensation of chief compliance officer | 411 | &nbsp;&nbsp; 139 | &nbsp;&nbsp; 33 |
| IRS Closing Agreement for European Union tax reclaim |  | &nbsp;&nbsp; 1458706 | &nbsp;&nbsp; 1347399 |
| Compensation of board members | 3260 | &nbsp;&nbsp; 1729 | &nbsp;&nbsp; 1161 |
| Other expenses | 62300 | &nbsp;&nbsp; 75178 | &nbsp;&nbsp; 37152 |
| Deferred compensation of board members | 4813757 | &nbsp;&nbsp; 2158681 | &nbsp;&nbsp; 151690 |
| Total liabilities | 6776626 | &nbsp;&nbsp; 4813672 | &nbsp;&nbsp; 1615458 |
| **Net assets applicable to outstanding capital stock** | **$2435860719** | &nbsp;&nbsp; **$805895861** | &nbsp;&nbsp; **$199839273** |
| **Represented by** |  |  |  |
| Paid in capital | 2009749212 | &nbsp;&nbsp; 659108166 | &nbsp;&nbsp; 165014480 |
| Total distributable earnings (loss) | 426111507 | &nbsp;&nbsp; 146787695 | &nbsp;&nbsp; 34824793 |
| **Total - representing net assets applicable to outstanding capital stock** | **$2435860719** | &nbsp;&nbsp; **$805895861** | &nbsp;&nbsp; **$199839273** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Assets and Liabilities (continued)

December 31, 2025

---

| | | | |
|:---|:---|:---|:---|
|  | **Columbia**<br> **Acorn**<sup>®</sup><br> **Fund**<br>| **Columbia**<br> **Acorn**<br> **International**<sup>®</sup><br>| **Columbia**<br> **Acorn**<br> **International**<br> **Select**<sup>SM</sup><br>|
| **Class A** |  |  |  |
| Net assets | $475067589 | &nbsp;&nbsp; $115157575 | &nbsp;&nbsp; $116232705 |
| Shares outstanding | 53123533 | &nbsp;&nbsp; 5042393 | &nbsp;&nbsp; 4090352 |
| Net asset value per share | $8.94 | &nbsp;&nbsp; $22.84 | &nbsp;&nbsp; $28.42 |
| Maximum sales charge  | 5.75% | &nbsp;&nbsp; 5.75% | &nbsp;&nbsp; 5.75% |
| Maximum offering price per share (calculated by dividing the net asset value per share by 1.0 minus the <br> maximum sales charge for Class A shares)<br>| $9.49 | &nbsp;&nbsp; $24.23 | &nbsp;&nbsp; $30.15 |
| **Class C** |  |  |  |
| Net assets | $5068589 | &nbsp;&nbsp; $— | &nbsp;&nbsp; $— |
| Shares outstanding | 414737 | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Net asset value per share | $12.22 | &nbsp;&nbsp; $— | &nbsp;&nbsp; $— |
| **Institutional Class** |  |  |  |
| Net assets | $1604234921 | &nbsp;&nbsp; $515250718 | &nbsp;&nbsp; $58414589 |
| Shares outstanding | 122328201 | &nbsp;&nbsp; 22414680 | &nbsp;&nbsp; 2011732 |
| Net asset value per share | $13.11 | &nbsp;&nbsp; $22.99 | &nbsp;&nbsp; $29.04 |
| **Institutional 2 Class** |  |  |  |
| Net assets | $25586221 | &nbsp;&nbsp; $17027583 | &nbsp;&nbsp; $3185122 |
| Shares outstanding | 1766715 | &nbsp;&nbsp; 741211 | &nbsp;&nbsp; 108417 |
| Net asset value per share | $14.48 | &nbsp;&nbsp; $22.97 | &nbsp;&nbsp; $29.38 |
| **Institutional 3 Class** |  |  |  |
| Net assets | $23301297 | &nbsp;&nbsp; $63201288 | &nbsp;&nbsp; $9382122 |
| Shares outstanding | 1579506 | &nbsp;&nbsp; 2691388 | &nbsp;&nbsp; 319443 |
| Net asset value per share | $14.75 | &nbsp;&nbsp; $23.48 | &nbsp;&nbsp; $29.37 |
| **Class S** |  |  |  |
| Net assets | $302602102 | &nbsp;&nbsp; $95258697 | &nbsp;&nbsp; $12624735 |
| Shares outstanding | 23072127 | &nbsp;&nbsp; 4143626 | &nbsp;&nbsp; 434764 |
| Net asset value per share | $13.12 | &nbsp;&nbsp; $22.99 | &nbsp;&nbsp; $29.04 |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Assets and Liabilities (continued)

December 31, 2025

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
|  | **Columbia** <br>**Thermostat** <br>**Fund**<sup>SM</sup><br>| **Columbia** <br>**Acorn** <br>**European** <br>**Fund**<sup>SM</sup><br>|
| **Assets** |  |  |
| Investments in securities, at value |  |  |
| Unaffiliated issuers (cost $—, $30,639,293, respectively) | $— | &nbsp;&nbsp; $35825406 |
| Affiliated issuers (cost $1,203,222,322, $326,153, respectively) | 1297185426 | &nbsp;&nbsp; 326154 |
| Receivable for: |  |  |
| Capital shares sold | 555264 | &nbsp;&nbsp; 375283 |
| Dividends | 3498708 | &nbsp;&nbsp; 20981 |
| Foreign tax reclaims |  | &nbsp;&nbsp; 225149 |
| Expense reimbursement due from Investment Manager |  | &nbsp;&nbsp; 608 |
| Due from custodian |  | &nbsp;&nbsp; 35216 |
| Prepaid expenses | 3585 | &nbsp;&nbsp; 1679 |
| Total assets | 1301242983 | &nbsp;&nbsp; 36810476 |
| **Liabilities** |  |  |
| Foreign currency (cost $—, $34,569, respectively) |  | &nbsp;&nbsp; 34569 |
| Payable for: |  |  |
| Investments purchased | 3484594 | &nbsp;&nbsp; 2855 |
| Capital shares redeemed | 423519 | &nbsp;&nbsp; 24631 |
| Management services fees | 3565 | &nbsp;&nbsp; 969 |
| Distribution and/or service fees | 4963 | &nbsp;&nbsp; 161 |
| Transfer agent fees | 112162 | &nbsp;&nbsp; 3943 |
| Compensation of chief compliance officer | 208 | &nbsp;&nbsp; 6 |
| Accounting services fees | 4089 | &nbsp;&nbsp; 14100 |
| Custodian fees | 1284 | &nbsp;&nbsp; 11660 |
| Compensation of board members | 2168 | &nbsp;&nbsp; 1013 |
| Other expenses | 48021 | &nbsp;&nbsp; 6125 |
| Deferred compensation of board members | 511811 | &nbsp;&nbsp; 38070 |
| Total liabilities | 4596384 | &nbsp;&nbsp; 138102 |
| **Net assets applicable to outstanding capital stock** | **$1296646599** | &nbsp;&nbsp; **$36672374** |
| **Represented by** |  |  |
| Paid in capital | 1266323036 | &nbsp;&nbsp; 31908852 |
| Total distributable earnings (loss) | 30323563 | &nbsp;&nbsp; 4763522 |
| **Total - representing net assets applicable to outstanding capital stock** | **$1296646599** | &nbsp;&nbsp; **$36672374** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Assets and Liabilities (continued)

December 31, 2025

---

| | | |
|:---|:---|:---|
|  | **Columbia**<br> **Thermostat**<br> **Fund**<sup>SM</sup><br>| **Columbia**<br> **Acorn**<br> **European**<br> **Fund**<sup>SM</sup><br>|
| **Class A** |  |  |
| Net assets | $390530505 | &nbsp;&nbsp; $23744500 |
| Shares outstanding | 21556894 | &nbsp;&nbsp; 975385 |
| Net asset value per share | $18.12 | &nbsp;&nbsp; $24.34 |
| Maximum sales charge  | 5.75% | &nbsp;&nbsp; 5.75% |
| Maximum offering price per share (calculated by dividing the net asset value per share by 1.0 minus the maximum sales charge for <br> Class A shares)<br>| $19.23 | &nbsp;&nbsp; $25.82 |
| **Class C** |  |  |
| Net assets | $82776095 | &nbsp;&nbsp; $— |
| Shares outstanding | 4537476 | &nbsp;&nbsp; — |
| Net asset value per share | $18.24 | &nbsp;&nbsp; $— |
| **Institutional Class** |  |  |
| Net assets | $702762296 | &nbsp;&nbsp; $12927874 |
| Shares outstanding | 39614610 | &nbsp;&nbsp; 525727 |
| Net asset value per share | $17.74 | &nbsp;&nbsp; $24.59 |
| **Institutional 2 Class** |  |  |
| Net assets | $92061165 | &nbsp;&nbsp; $— |
| Shares outstanding | 5138263 | &nbsp;&nbsp; — |
| Net asset value per share | $17.92 | &nbsp;&nbsp; $— |
| **Institutional 3 Class** |  |  |
| Net assets | $15711440 | &nbsp;&nbsp; $— |
| Shares outstanding | 878904 | &nbsp;&nbsp; — |
| Net asset value per share | $17.88 | &nbsp;&nbsp; $— |
| **Class S** |  |  |
| Net assets | $12805098 | &nbsp;&nbsp; $— |
| Shares outstanding | 721810 | &nbsp;&nbsp; — |
| Net asset value per share | $17.74 | &nbsp;&nbsp; $— |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Operations

Year Ended December 31, 2025

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | |
|:---|:---|:---|:---|
|  | **Columbia** <br>**Acorn**<sup>®</sup> <br>**Fund**<br>| **Columbia** <br>**Acorn** <br>**International**<sup>®</sup><br>| **Columbia** <br>**Acorn** <br>**International** <br>**Select**<sup>SM</sup><br>|
| **Net investment income** |  |  |  |
| Income: |  |  |  |
| Dividends — unaffiliated issuers | $6855753 | &nbsp;&nbsp; $17918801 | &nbsp;&nbsp; $4621843 |
| Dividends — affiliated issuers | 2711613 | &nbsp;&nbsp; 336167 | &nbsp;&nbsp; 96429 |
| Income from securities lending — net | 384593 | &nbsp;&nbsp; 59185 | &nbsp;&nbsp; 836 |
| European Union tax reclaim | 1212619 | &nbsp;&nbsp; 4300633 | &nbsp;&nbsp; 3965521 |
| Foreign taxes withheld | (21650)<br>| &nbsp;&nbsp; (1291273)<br>| &nbsp;&nbsp; (413069)<br>|
| IRS closing agreement for European Union tax reclaim |  | &nbsp;&nbsp; (1458706)<br>| &nbsp;&nbsp; (1347399)<br>|
| Total income | 11142928 | &nbsp;&nbsp; 19864807 | &nbsp;&nbsp; 6924161 |
| Expenses: |  |  |  |
| Management services fees | 17699069 | &nbsp;&nbsp; 7533596 | &nbsp;&nbsp; 1715600 |
| Distribution and/or service fees |  |  |  |
| Class A | 1221225 | &nbsp;&nbsp; 310804 | &nbsp;&nbsp; 287983 |
| Class C | 57542 | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Transfer agent fees |  |  |  |
| Class A | 420011 | &nbsp;&nbsp; 137641 | &nbsp;&nbsp; 217758 |
| Class C | 4936 | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Institutional Class | 1401691 | &nbsp;&nbsp; 600325 | &nbsp;&nbsp; 108174 |
| Institutional 2 Class | 13391 | &nbsp;&nbsp; 9785 | &nbsp;&nbsp; 1960 |
| Institutional 3 Class | 1340 | &nbsp;&nbsp; 4127 | &nbsp;&nbsp; 423 |
| Class S | 267957 | &nbsp;&nbsp; 119270 | &nbsp;&nbsp; 23704 |
| Administration fees | 322198 | &nbsp;&nbsp; 110533 | &nbsp;&nbsp; 23974 |
| Custodian fees | 18466 | &nbsp;&nbsp; 84144 | &nbsp;&nbsp; 24024 |
| Printing and postage fees | 111630 | &nbsp;&nbsp; 89433 | &nbsp;&nbsp; 48975 |
| Registration fees | 97431 | &nbsp;&nbsp; 82166 | &nbsp;&nbsp; 78614 |
| Accounting services fees | 28991 | &nbsp;&nbsp; 39766 | &nbsp;&nbsp; 35117 |
| Legal fees | 69221 | &nbsp;&nbsp; 27544 | &nbsp;&nbsp; 18624 |
| Line of credit interest |  | &nbsp;&nbsp; 4275 | &nbsp;&nbsp; 60 |
| Compensation of chief compliance officer | 372 | &nbsp;&nbsp; 120 | &nbsp;&nbsp; 30 |
| Compensation of board members | 70633 | &nbsp;&nbsp; 30037 | &nbsp;&nbsp; 14097 |
| Deferred compensation of board members | 261690 | &nbsp;&nbsp; 118833 | &nbsp;&nbsp; 14940 |
| Other | 130074 | &nbsp;&nbsp; 121013 | &nbsp;&nbsp; 64461 |
| Total expenses | 22197868 | &nbsp;&nbsp; 9423412 | &nbsp;&nbsp; 2678518 |
| Fees waived or expenses reimbursed by Investment Manager and its affiliates | (609314)<br>| &nbsp;&nbsp; (831097)<br>| &nbsp;&nbsp; (685120)<br>|
| Fees waived by transfer agent |  |  |  |
| Institutional 2 Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (79)<br>|
| Institutional 3 Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (146)<br>|
| Expense reduction | (4994)<br>| &nbsp;&nbsp; (3851)<br>| &nbsp;&nbsp; (5620)<br>|
| Total net expenses | 21583560 | &nbsp;&nbsp; 8588464 | &nbsp;&nbsp; 1987553 |
| **Net investment income (loss)** | (10440632)<br>| &nbsp;&nbsp; 11276343 | &nbsp;&nbsp; 4936608 |
| **Realized and unrealized gain (loss) — net** |  |  |  |
| Net realized gain (loss) on: |  |  |  |
| Investments — unaffiliated issuers | 203989324 | &nbsp;&nbsp; 29651923 | &nbsp;&nbsp; 10446816 |
| Investments — affiliated issuers | 621021 | &nbsp;&nbsp; (1405)<br>| &nbsp;&nbsp; 534 |
| Foreign currency translations |  | &nbsp;&nbsp; (144433)<br>| &nbsp;&nbsp; 45735 |
| Net realized gain | 204610345 | &nbsp;&nbsp; 29506085 | &nbsp;&nbsp; 10493085 |
| Net change in unrealized appreciation (depreciation) on: |  |  |  |
| Investments — unaffiliated issuers | (83945647)<br>| &nbsp;&nbsp; 63705708 | &nbsp;&nbsp; 20751778 |
| Investments — affiliated issuers | (3779387)<br>| &nbsp;&nbsp; 176 | &nbsp;&nbsp; (169)<br>|
| Foreign currency translations | 1 | &nbsp;&nbsp; 228399 | &nbsp;&nbsp; 70013 |
| Foreign capital gains tax |  | &nbsp;&nbsp; — | &nbsp;&nbsp; 270730 |
| Net change in unrealized appreciation (depreciation) | (87725033)<br>| &nbsp;&nbsp; 63934283 | &nbsp;&nbsp; 21092352 |
| Net realized and unrealized gain | 116885312 | &nbsp;&nbsp; 93440368 | &nbsp;&nbsp; 31585437 |
| **Net increase in net assets resulting from operations** | **$106444680** | &nbsp;&nbsp; **$104716711** | &nbsp;&nbsp; **$36522045** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Operations (continued)

Year Ended December 31, 2025

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
|  | **Columbia** <br>**Thermostat** <br>**Fund**<sup>SM</sup><br>| **Columbia** <br>**Acorn** <br>**European** <br>**Fund**<sup>SM</sup><br>|
| **Net investment income** |  |  |
| Income: |  |  |
| Dividends — unaffiliated issuers | $— | &nbsp;&nbsp; $1073732 |
| Dividends — affiliated issuers | 41204535 | &nbsp;&nbsp; 18031 |
| Income from securities lending — net |  | &nbsp;&nbsp; 1310 |
| Foreign taxes withheld |  | &nbsp;&nbsp; (99361)<br>|
| Total income | 41204535 | &nbsp;&nbsp; 993712 |
| Expenses: |  |  |
| Management services fees | 1237358 | &nbsp;&nbsp; 395935 |
| Distribution and/or service fees |  |  |
| Class A | 968282 | &nbsp;&nbsp; 60005 |
| Class C | 852044 | &nbsp;&nbsp; — |
| Transfer agent fees |  |  |
| Class A | 358127 | &nbsp;&nbsp; 29239 |
| Class C | 78811 | &nbsp;&nbsp; — |
| Institutional Class | 607758 | &nbsp;&nbsp; 18917 |
| Institutional 2 Class | 44450 | &nbsp;&nbsp; — |
| Institutional 3 Class | 885 | &nbsp;&nbsp; — |
| Class S | 11681 | &nbsp;&nbsp; — |
| Administration fees | 146580 | &nbsp;&nbsp; 5105 |
| Custodian fees | 4122 | &nbsp;&nbsp; 40237 |
| Printing and postage fees | 90447 | &nbsp;&nbsp; 22418 |
| Registration fees | 114044 | &nbsp;&nbsp; 40900 |
| Accounting services fees | 8398 | &nbsp;&nbsp; 28991 |
| Legal fees | 38507 | &nbsp;&nbsp; 15823 |
| Line of credit interest | 539 | &nbsp;&nbsp; 175 |
| Compensation of chief compliance officer | 190 | &nbsp;&nbsp; 5 |
| Compensation of board members | 37489 | &nbsp;&nbsp; 10578 |
| Deferred compensation of board members | 61137 | &nbsp;&nbsp; 6355 |
| Other | 59936 | &nbsp;&nbsp; 4315 |
| Total expenses | 4720785 | &nbsp;&nbsp; 678998 |
| Fees waived or expenses reimbursed by Investment Manager and its affiliates | (49804)<br>| &nbsp;&nbsp; (187213)<br>|
| Fees waived by transfer agent |  |  |
| Institutional 2 Class | (3567)<br>| &nbsp;&nbsp; — |
| Institutional 3 Class | (257)<br>| &nbsp;&nbsp; — |
| Expense reduction | (80)<br>| &nbsp;&nbsp; (40)<br>|
| Total net expenses | 4667077 | &nbsp;&nbsp; 491745 |
| **Net investment income** | 36537458 | &nbsp;&nbsp; 501967 |
| **Realized and unrealized gain (loss) — net** |  |  |
| Net realized gain (loss) on: |  |  |
| Investments — unaffiliated issuers |  | &nbsp;&nbsp; 11982401 |
| Investments — affiliated issuers | 29660520 | &nbsp;&nbsp; (185)<br>|
| Capital gain distributions from underlying affiliated funds | 37228478 | &nbsp;&nbsp; — |
| Foreign currency translations |  | &nbsp;&nbsp; (2868)<br>|
| Net realized gain | 66888998 | &nbsp;&nbsp; 11979348 |
| Net change in unrealized appreciation (depreciation) on: |  |  |
| Investments — unaffiliated issuers |  | &nbsp;&nbsp; (4187354)<br>|
| Investments — affiliated issuers | 67464244 | &nbsp;&nbsp; 1 |
| Foreign currency translations |  | &nbsp;&nbsp; 24621 |
| Net change in unrealized appreciation (depreciation) | 67464244 | &nbsp;&nbsp; (4162732)<br>|
| Net realized and unrealized gain | 134353242 | &nbsp;&nbsp; 7816616 |
| **Net increase in net assets resulting from operations** | **$170890700** | &nbsp;&nbsp; **$8318583** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia Acorn** <br>**International**<sup>®</sup> | **Columbia Acorn** <br>**International**<sup>®</sup> |
|  | **Year Ended** <br>**December 31, 2025**<br>| **Year Ended** <br>**December 31, 2024**<br>| **Year Ended** <br>**December 31, 2025**<br>| **Year Ended** <br>**December 31, 2024**<br>|
| **Operations** |  |  |  |  |
| Net investment income (loss) | $(10440632)<br>| &nbsp;&nbsp; $(15049222)<br>| &nbsp;&nbsp; $11276343 | &nbsp;&nbsp; $10026120 |
| Net realized gain | 204610345 | &nbsp;&nbsp; 354316937 | &nbsp;&nbsp; 29506085 | &nbsp;&nbsp; 84164253 |
| Net change in unrealized appreciation (depreciation) | (87725033)<br>| &nbsp;&nbsp; 33556369 | &nbsp;&nbsp; 63934283 | &nbsp;&nbsp; (139384521)<br>|
| Net increase (decrease) in net assets resulting from operations | 106444680 | &nbsp;&nbsp; 372824084 | &nbsp;&nbsp; 104716711 | &nbsp;&nbsp; (45194148)<br>|
| **Distributions to shareholders** |  |  |  |  |
| Net investment income and net realized gains  |  |  |  |  |
| Class A |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (6667661)<br>| &nbsp;&nbsp; (14776573)<br>|
| Advisor Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (187821)<br>|
| Institutional Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (30609530)<br>| &nbsp;&nbsp; (70673340)<br>|
| Institutional 2 Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (1031592)<br>| &nbsp;&nbsp; (2116606)<br>|
| Institutional 3 Class |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (3914636)<br>| &nbsp;&nbsp; (12977717)<br>|
| Class S |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (5908781)<br>| &nbsp;&nbsp; (9229839)<br>|
| Total distributions to shareholders |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (48132200)<br>| &nbsp;&nbsp; (109961896)<br>|
| Decrease in net assets from capital stock activity | (399417644)<br>| &nbsp;&nbsp; (426753331)<br>| &nbsp;&nbsp; (134992008)<br>| &nbsp;&nbsp; (118727568)<br>|
| Total decrease in net assets | (292972964)<br>| &nbsp;&nbsp; (53929247)<br>| &nbsp;&nbsp; (78407497)<br>| &nbsp;&nbsp; (273883612)<br>|
| Net assets at beginning of year | 2728833683 | &nbsp;&nbsp; 2782762930 | &nbsp;&nbsp; 884303358 | &nbsp;&nbsp; 1158186970 |
| **Net assets at end of year** | **$2435860719** | &nbsp;&nbsp; **$2728833683** | &nbsp;&nbsp; **$805895861** | &nbsp;&nbsp; **$884303358** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets (continued)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> |
|  | **Year Ended** <br>**December 31, 2025**<br>| **Year Ended** <br>**December 31, 2024**<br>| **Year Ended** <br>**December 31, 2025**<br>| **Year Ended** <br>**December 31, 2024**<br>|
| **Operations** |  |  |  |  |
| Net investment income | $4936608 | &nbsp;&nbsp; $2095239 | &nbsp;&nbsp; $36537458 | &nbsp;&nbsp; $37470246 |
| Net realized gain | 10493085 | &nbsp;&nbsp; 17965244 | &nbsp;&nbsp; 66888998 | &nbsp;&nbsp; 22317876 |
| Net change in unrealized appreciation (depreciation) | 21092352 | &nbsp;&nbsp; (19497864)<br>| &nbsp;&nbsp; 67464244 | &nbsp;&nbsp; 34872187 |
| Net increase in net assets resulting from operations | 36522045 | &nbsp;&nbsp; 562619 | &nbsp;&nbsp; 170890700 | &nbsp;&nbsp; 94660309 |
| **Distributions to shareholders** |  |  |  |  |
| Net investment income and net realized gains  |  |  |  |  |
| Class A | (7295152)<br>| &nbsp;&nbsp; (1124318)<br>| &nbsp;&nbsp; (11816759)<br>| &nbsp;&nbsp; (12416154)<br>|
| Advisor Class |  | &nbsp;&nbsp; (10754)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; (302495)<br>|
| Class C |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (1943530)<br>| &nbsp;&nbsp; (2211271)<br>|
| Institutional Class | (3858993)<br>| &nbsp;&nbsp; (826746)<br>| &nbsp;&nbsp; (23137224)<br>| &nbsp;&nbsp; (21710377)<br>|
| Institutional 2 Class | (222099)<br>| &nbsp;&nbsp; (56532)<br>| &nbsp;&nbsp; (3020417)<br>| &nbsp;&nbsp; (2679962)<br>|
| Institutional 3 Class | (626094)<br>| &nbsp;&nbsp; (114637)<br>| &nbsp;&nbsp; (502497)<br>| &nbsp;&nbsp; (372731)<br>|
| Class S | (835976)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; (426037)<br>| &nbsp;&nbsp; (398576)<br>|
| Total distributions to shareholders | (12838314)<br>| &nbsp;&nbsp; (2132987)<br>| &nbsp;&nbsp; (40846464)<br>| &nbsp;&nbsp; (40091566)<br>|
| Decrease in net assets from capital stock activity | (13471249)<br>| &nbsp;&nbsp; (33869049)<br>| &nbsp;&nbsp; (32023490)<br>| &nbsp;&nbsp; (198986914)<br>|
| Total increase (decrease) in net assets | 10212482 | &nbsp;&nbsp; (35439417)<br>| &nbsp;&nbsp; 98020746 | &nbsp;&nbsp; (144418171)<br>|
| Net assets at beginning of year | 189626791 | &nbsp;&nbsp; 225066208 | &nbsp;&nbsp; 1198625853 | &nbsp;&nbsp; 1343044024 |
| **Net assets at end of year** | **$199839273** | &nbsp;&nbsp; **$189626791** | &nbsp;&nbsp; **$1296646599** | &nbsp;&nbsp; **$1198625853** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets (continued)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
|  | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> |
|  | **Year Ended** <br>**December 31, 2025**<br>| **Year Ended** <br>**December 31, 2024**<br>|
| **Operations** |  |  |
| Net investment income | $501967 | &nbsp;&nbsp; $88737 |
| Net realized gain | 11979348 | &nbsp;&nbsp; 12835372 |
| Net change in unrealized appreciation (depreciation) | (4162732)<br>| &nbsp;&nbsp; (14829291)<br>|
| Net increase (decrease) in net assets resulting from operations | 8318583 | &nbsp;&nbsp; (1905182)<br>|
| **Distributions to shareholders** |  |  |
| Net investment income and net realized gains  |  |  |
| Class A | (4181024)<br>| &nbsp;&nbsp; (598281)<br>|
| Advisor Class |  | &nbsp;&nbsp; (15596)<br>|
| Institutional Class | (2321395)<br>| &nbsp;&nbsp; (488108)<br>|
| Total distributions to shareholders | (6502419)<br>| &nbsp;&nbsp; (1101985)<br>|
| Decrease in net assets from capital stock activity | (6253259)<br>| &nbsp;&nbsp; (16527056)<br>|
| Total decrease in net assets | (4437095)<br>| &nbsp;&nbsp; (19534223)<br>|
| Net assets at beginning of year | 41109469 | &nbsp;&nbsp; 60643692 |
| **Net assets at end of year** | **$36672374** | &nbsp;&nbsp; **$41109469** |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets (continued)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia** <br>**Acorn**<sup>®</sup> **Fund** | **Columbia Acorn** <br>**International**<sup>®</sup> | **Columbia Acorn** <br>**International**<sup>®</sup> | **Columbia Acorn** <br>**International**<sup>®</sup> | **Columbia Acorn** <br>**International**<sup>®</sup> |
|  | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** |
|  | **December 31, 2025**  | **December 31, 2025**  | **December 31, 2024**  | **December 31, 2024**  | **December 31, 2025**  | **December 31, 2025**  | **December 31, 2024**  | **December 31, 2024**  |
|  | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** |
| **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** |
| Class A |  |  |  |  |  |  |  |  |
| Shares sold | 951099 | &nbsp;&nbsp; 7819057 | &nbsp;&nbsp; 1132352 | &nbsp;&nbsp; 9163800 | &nbsp;&nbsp; 158477 | &nbsp;&nbsp; 3698642 | &nbsp;&nbsp; 338163 | &nbsp;&nbsp; 8410184 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 276003 | &nbsp;&nbsp; 6373479 | &nbsp;&nbsp; 623582 | &nbsp;&nbsp; 14150032 |
| Shares redeemed | (11525144)<br>| &nbsp;&nbsp; (96468719)<br>| &nbsp;&nbsp; (13562866)<br>| &nbsp;&nbsp; (109021278)<br>| &nbsp;&nbsp; (1115333)<br>| &nbsp;&nbsp; (25831097)<br>| &nbsp;&nbsp; (1361129)<br>| &nbsp;&nbsp; (33790944)<br>|
| Net decrease | (10574045)<br>| &nbsp;&nbsp; (88649662)<br>| &nbsp;&nbsp; (12430514)<br>| &nbsp;&nbsp; (99857478)<br>| &nbsp;&nbsp; (680853)<br>| &nbsp;&nbsp; (15758976)<br>| &nbsp;&nbsp; (399384)<br>| &nbsp;&nbsp; (11230728)<br>|
| Advisor Class |  |  |  |  |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp; — | &nbsp;&nbsp; 218852 | &nbsp;&nbsp; 2732848 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 22985 | &nbsp;&nbsp; 590751 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 7258 | &nbsp;&nbsp; 187630 |
| Shares redeemed |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (3279577)<br>| &nbsp;&nbsp; (46124474)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (248274)<br>| &nbsp;&nbsp; (6151410)<br>|
| Net decrease |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (3060725)<br>| &nbsp;&nbsp; (43391626)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (218031)<br>| &nbsp;&nbsp; (5373029)<br>|
| Class C |  |  |  |  |  |  |  |  |
| Shares sold | 29218 | &nbsp;&nbsp; 327595 | &nbsp;&nbsp; 46214 | &nbsp;&nbsp; 496832 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 1368 | &nbsp;&nbsp; 29826 |
| Shares redeemed | (231412)<br>| &nbsp;&nbsp; (2625146)<br>| &nbsp;&nbsp; (294421)<br>| &nbsp;&nbsp; (3234271)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (148003)<br>| &nbsp;&nbsp; (3228484)<br>|
| Net decrease | (202194)<br>| &nbsp;&nbsp; (2297551)<br>| &nbsp;&nbsp; (248207)<br>| &nbsp;&nbsp; (2737439)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (146635)<br>| &nbsp;&nbsp; (3198658)<br>|
| Institutional Class |  |  |  |  |  |  |  |  |
| Shares sold | 1858214 | &nbsp;&nbsp; 22132141 | &nbsp;&nbsp; 4779528 | &nbsp;&nbsp; 60466900 | &nbsp;&nbsp; 220580 | &nbsp;&nbsp; 5124881 | &nbsp;&nbsp; 379620 | &nbsp;&nbsp; 9275114 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 1174703 | &nbsp;&nbsp; 27269315 | &nbsp;&nbsp; 2738250 | &nbsp;&nbsp; 63070993 |
| Shares redeemed | (20884267)<br>| &nbsp;&nbsp; (258401731)<br>| &nbsp;&nbsp; (56498495)<br>| &nbsp;&nbsp; (679545275)<br>| &nbsp;&nbsp; (3214666)<br>| &nbsp;&nbsp; (74963235)<br>| &nbsp;&nbsp; (11509843)<br>| &nbsp;&nbsp; (296693997)<br>|
| Net decrease | (19026053)<br>| &nbsp;&nbsp; (236269590)<br>| &nbsp;&nbsp; (51718967)<br>| &nbsp;&nbsp; (619078375)<br>| &nbsp;&nbsp; (1819383)<br>| &nbsp;&nbsp; (42569039)<br>| &nbsp;&nbsp; (8391973)<br>| &nbsp;&nbsp; (224347890)<br>|
| Institutional 2 Class |  |  |  |  |  |  |  |  |
| Shares sold | 438239 | &nbsp;&nbsp; 5939790 | &nbsp;&nbsp; 350551 | &nbsp;&nbsp; 4595267 | &nbsp;&nbsp; 88396 | &nbsp;&nbsp; 2036592 | &nbsp;&nbsp; 66030 | &nbsp;&nbsp; 1649754 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 44416 | &nbsp;&nbsp; 1030248 | &nbsp;&nbsp; 92289 | &nbsp;&nbsp; 2113154 |
| Shares redeemed | (655112)<br>| &nbsp;&nbsp; (8893741)<br>| &nbsp;&nbsp; (751649)<br>| &nbsp;&nbsp; (9623144)<br>| &nbsp;&nbsp; (153552)<br>| &nbsp;&nbsp; (3623812)<br>| &nbsp;&nbsp; (290130)<br>| &nbsp;&nbsp; (7229364)<br>|
| Net decrease | (216873)<br>| &nbsp;&nbsp; (2953951)<br>| &nbsp;&nbsp; (401098)<br>| &nbsp;&nbsp; (5027877)<br>| &nbsp;&nbsp; (20740)<br>| &nbsp;&nbsp; (556972)<br>| &nbsp;&nbsp; (131811)<br>| &nbsp;&nbsp; (3466456)<br>|
| Institutional 3 Class |  |  |  |  |  |  |  |  |
| Shares sold | 303595 | &nbsp;&nbsp; 4092843 | &nbsp;&nbsp; 341360 | &nbsp;&nbsp; 4439835 | &nbsp;&nbsp; 222946 | &nbsp;&nbsp; 5229295 | &nbsp;&nbsp; 461541 | &nbsp;&nbsp; 11337102 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 164054 | &nbsp;&nbsp; 3894524 | &nbsp;&nbsp; 383395 | &nbsp;&nbsp; 8931728 |
| Shares redeemed | (826365)<br>| &nbsp;&nbsp; (11165551)<br>| &nbsp;&nbsp; (534626)<br>| &nbsp;&nbsp; (7078513)<br>| &nbsp;&nbsp; (2580327)<br>| &nbsp;&nbsp; (62384959)<br>| &nbsp;&nbsp; (971545)<br>| &nbsp;&nbsp; (24990518)<br>|
| Net decrease | (522770)<br>| &nbsp;&nbsp; (7072708)<br>| &nbsp;&nbsp; (193266)<br>| &nbsp;&nbsp; (2638678)<br>| &nbsp;&nbsp; (2193327)<br>| &nbsp;&nbsp; (53261140)<br>| &nbsp;&nbsp; (126609)<br>| &nbsp;&nbsp; (4721688)<br>|
| Class R |  |  |  |  |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 1674 | &nbsp;&nbsp; 40933 |
| Shares redeemed |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (84904)<br>| &nbsp;&nbsp; (2070566)<br>|
| Net decrease |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (83230)<br>| &nbsp;&nbsp; (2029633)<br>|
| Class S |  |  |  |  |  |  |  |  |
| Shares sold | 171779 | &nbsp;&nbsp; 2114909 | &nbsp;&nbsp; 30814407 | &nbsp;&nbsp; 380431067 | &nbsp;&nbsp; 17681 | &nbsp;&nbsp; 410344 | &nbsp;&nbsp; 5384804 | &nbsp;&nbsp; 142655849 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 254105 | &nbsp;&nbsp; 5904535 | &nbsp;&nbsp; 425476 | &nbsp;&nbsp; 9220057 |
| Shares redeemed | (5249923)<br>| &nbsp;&nbsp; (64289091)<br>| &nbsp;&nbsp; (2664136)<br>| &nbsp;&nbsp; (34452925)<br>| &nbsp;&nbsp; (1253813)<br>| &nbsp;&nbsp; (29160760)<br>| &nbsp;&nbsp; (684627)<br>| &nbsp;&nbsp; (16235392)<br>|
| Net increase (decrease) | (5078144)<br>| &nbsp;&nbsp; (62174182)<br>| &nbsp;&nbsp; 28150271 | &nbsp;&nbsp; 345978142 | &nbsp;&nbsp; (982027)<br>| &nbsp;&nbsp; (22845881)<br>| &nbsp;&nbsp; 5125653 | &nbsp;&nbsp; 135640514 |
| **Total net decrease** | **(35620079)**<br>| &nbsp;&nbsp; **(399417644)**<br>| &nbsp;&nbsp; **(39902506)**<br>| &nbsp;&nbsp; **(426753331)**<br>| &nbsp;&nbsp; **(5696330)**<br>| &nbsp;&nbsp; **(134992008)**<br>| &nbsp;&nbsp; **(4372020)**<br>| &nbsp;&nbsp; **(118727568)**<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets (continued)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia Acorn** <br>**International Select**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> | **Columbia** <br>**Thermostat Fund**<sup>SM</sup> |
|  | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** |
|  | **December 31, 2025**  | **December 31, 2025**  | **December 31, 2024**  | **December 31, 2024**  | **December 31, 2025**  | **December 31, 2025**  | **December 31, 2024**  | **December 31, 2024**  |
|  | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** |
| **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** |
| Class A |  |  |  |  |  |  |  |  |
| Shares sold | 74028 | &nbsp;&nbsp; 2038646 | &nbsp;&nbsp; 72601 | &nbsp;&nbsp; 1877055 | &nbsp;&nbsp; 1423314 | &nbsp;&nbsp; 24753996 | &nbsp;&nbsp; 1560668 | &nbsp;&nbsp; 25017144 |
| Distributions reinvested | 242611 | &nbsp;&nbsp; 6732213 | &nbsp;&nbsp; 38497 | &nbsp;&nbsp; 1033246 | &nbsp;&nbsp; 609337 | &nbsp;&nbsp; 10937780 | &nbsp;&nbsp; 703749 | &nbsp;&nbsp; 11451576 |
| Shares redeemed | (619297)<br>| &nbsp;&nbsp; (17078490)<br>| &nbsp;&nbsp; (745084)<br>| &nbsp;&nbsp; (19426483)<br>| &nbsp;&nbsp; (4176884)<br>| &nbsp;&nbsp; (72336708)<br>| &nbsp;&nbsp; (5986998)<br>| &nbsp;&nbsp; (96073826)<br>|
| Net decrease | (302658)<br>| &nbsp;&nbsp; (8307631)<br>| &nbsp;&nbsp; (633986)<br>| &nbsp;&nbsp; (16516182)<br>| &nbsp;&nbsp; (2144233)<br>| &nbsp;&nbsp; (36644932)<br>| &nbsp;&nbsp; (3722581)<br>| &nbsp;&nbsp; (59605106)<br>|
| Advisor Class |  |  |  |  |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp; — | &nbsp;&nbsp; 8189 | &nbsp;&nbsp; 221213 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 1363908 | &nbsp;&nbsp; 21181473 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; 387 | &nbsp;&nbsp; 10723 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 19097 | &nbsp;&nbsp; 301351 |
| Shares redeemed |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (44025)<br>| &nbsp;&nbsp; (1173900)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (5875625)<br>| &nbsp;&nbsp; (96946631)<br>|
| Net decrease |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (35449)<br>| &nbsp;&nbsp; (941964)<br>| &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; (4492620)<br>| &nbsp;&nbsp; (75463807)<br>|
| Class C |  |  |  |  |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp; — | &nbsp;&nbsp; 642 | &nbsp;&nbsp; 13933 | &nbsp;&nbsp; 484619 | &nbsp;&nbsp; 8402402 | &nbsp;&nbsp; 457227 | &nbsp;&nbsp; 7299907 |
| Distributions reinvested |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 102437 | &nbsp;&nbsp; 1845917 | &nbsp;&nbsp; 126698 | &nbsp;&nbsp; 2073544 |
| Shares redeemed |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (48724)<br>| &nbsp;&nbsp; (1079132)<br>| &nbsp;&nbsp; (1410506)<br>| &nbsp;&nbsp; (24550141)<br>| &nbsp;&nbsp; (2287469)<br>| &nbsp;&nbsp; (36778190)<br>|
| Net decrease |  | &nbsp;&nbsp; — | &nbsp;&nbsp; (48082)<br>| &nbsp;&nbsp; (1065199)<br>| &nbsp;&nbsp; (823450)<br>| &nbsp;&nbsp; (14301822)<br>| &nbsp;&nbsp; (1703544)<br>| &nbsp;&nbsp; (27404739)<br>|
| Institutional Class |  |  |  |  |  |  |  |  |
| Shares sold | 96969 | &nbsp;&nbsp; 2719662 | &nbsp;&nbsp; 114467 | &nbsp;&nbsp; 3045470 | &nbsp;&nbsp; 7587833 | &nbsp;&nbsp; 129383845 | &nbsp;&nbsp; 10066666 | &nbsp;&nbsp; 161650690 |
| Distributions reinvested | 114146 | &nbsp;&nbsp; 3237025 | &nbsp;&nbsp; 26520 | &nbsp;&nbsp; 726909 | &nbsp;&nbsp; 1084114 | &nbsp;&nbsp; 19075249 | &nbsp;&nbsp; 1142666 | &nbsp;&nbsp; 18218419 |
| Shares redeemed | (313623)<br>| &nbsp;&nbsp; (8754629)<br>| &nbsp;&nbsp; (1089922)<br>| &nbsp;&nbsp; (29535423)<br>| &nbsp;&nbsp; (8227175)<br>| &nbsp;&nbsp; (139014453)<br>| &nbsp;&nbsp; (13641826)<br>| &nbsp;&nbsp; (215349951)<br>|
| Net increase (decrease) | (102508)<br>| &nbsp;&nbsp; (2797942)<br>| &nbsp;&nbsp; (948935)<br>| &nbsp;&nbsp; (25763044)<br>| &nbsp;&nbsp; 444772 | &nbsp;&nbsp; 9444641 | &nbsp;&nbsp; (2432494)<br>| &nbsp;&nbsp; (35480842)<br>|
| Institutional 2 Class |  |  |  |  |  |  |  |  |
| Shares sold | 7443 | &nbsp;&nbsp; 214579 | &nbsp;&nbsp; 10380 | &nbsp;&nbsp; 281427 | &nbsp;&nbsp; 1603212 | &nbsp;&nbsp; 27846184 | &nbsp;&nbsp; 1629460 | &nbsp;&nbsp; 25850054 |
| Distributions reinvested | 7742 | &nbsp;&nbsp; 222072 | &nbsp;&nbsp; 2039 | &nbsp;&nbsp; 56528 | &nbsp;&nbsp; 169865 | &nbsp;&nbsp; 3020417 | &nbsp;&nbsp; 166441 | &nbsp;&nbsp; 2679962 |
| Shares redeemed | (58801)<br>| &nbsp;&nbsp; (1656787)<br>| &nbsp;&nbsp; (80948)<br>| &nbsp;&nbsp; (2160394)<br>| &nbsp;&nbsp; (1413114)<br>| &nbsp;&nbsp; (23973410)<br>| &nbsp;&nbsp; (2646019)<br>| &nbsp;&nbsp; (41946646)<br>|
| Net increase (decrease) | (43616)<br>| &nbsp;&nbsp; (1220136)<br>| &nbsp;&nbsp; (68529)<br>| &nbsp;&nbsp; (1822439)<br>| &nbsp;&nbsp; 359963 | &nbsp;&nbsp; 6893191 | &nbsp;&nbsp; (850118)<br>| &nbsp;&nbsp; (13416630)<br>|
| Institutional 3 Class |  |  |  |  |  |  |  |  |
| Shares sold | 16529 | &nbsp;&nbsp; 473726 | &nbsp;&nbsp; 32621 | &nbsp;&nbsp; 887685 | &nbsp;&nbsp; 409985 | &nbsp;&nbsp; 7176180 | &nbsp;&nbsp; 116878 | &nbsp;&nbsp; 1868513 |
| Distributions reinvested | 21787 | &nbsp;&nbsp; 624933 | &nbsp;&nbsp; 4132 | &nbsp;&nbsp; 114544 | &nbsp;&nbsp; 28211 | &nbsp;&nbsp; 501056 | &nbsp;&nbsp; 23111 | &nbsp;&nbsp; 371235 |
| Shares redeemed | (49938)<br>| &nbsp;&nbsp; (1415597)<br>| &nbsp;&nbsp; (62603)<br>| &nbsp;&nbsp; (1700783)<br>| &nbsp;&nbsp; (219940)<br>| &nbsp;&nbsp; (3776809)<br>| &nbsp;&nbsp; (195591)<br>| &nbsp;&nbsp; (3100122)<br>|
| Net increase (decrease) | (11622)<br>| &nbsp;&nbsp; (316938)<br>| &nbsp;&nbsp; (25850)<br>| &nbsp;&nbsp; (698554)<br>| &nbsp;&nbsp; 218256 | &nbsp;&nbsp; 3900427 | &nbsp;&nbsp; (55602)<br>| &nbsp;&nbsp; (860374)<br>|
| Class S |  |  |  |  |  |  |  |  |
| Shares sold | 6123 | &nbsp;&nbsp; 170166 | &nbsp;&nbsp; 507130 | &nbsp;&nbsp; 14077388 | &nbsp;&nbsp; 3542 | &nbsp;&nbsp; 62126 | &nbsp;&nbsp; 832840 | &nbsp;&nbsp; 13754131 |
| Distributions reinvested | 29480 | &nbsp;&nbsp; 835976 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; 24222 | &nbsp;&nbsp; 426037 | &nbsp;&nbsp; 24942 | &nbsp;&nbsp; 398576 |
| Shares redeemed | (65092)<br>| &nbsp;&nbsp; (1834744)<br>| &nbsp;&nbsp; (42877)<br>| &nbsp;&nbsp; (1139055)<br>| &nbsp;&nbsp; (108243)<br>| &nbsp;&nbsp; (1803158)<br>| &nbsp;&nbsp; (55493)<br>| &nbsp;&nbsp; (908123)<br>|
| Net increase (decrease) | (29489)<br>| &nbsp;&nbsp; (828602)<br>| &nbsp;&nbsp; 464253 | &nbsp;&nbsp; 12938333 | &nbsp;&nbsp; (80479)<br>| &nbsp;&nbsp; (1314995)<br>| &nbsp;&nbsp; 802289 | &nbsp;&nbsp; 13244584 |
| **Total net decrease** | **(489893)**<br>| &nbsp;&nbsp; **(13471249)**<br>| &nbsp;&nbsp; **(1296578)**<br>| &nbsp;&nbsp; **(33869049)**<br>| &nbsp;&nbsp; **(2025171)**<br>| &nbsp;&nbsp; **(32023490)**<br>| &nbsp;&nbsp; **(12454670)**<br>| &nbsp;&nbsp; **(198986914)**<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Statement of Changes in Net Assets (continued)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> | **Columbia Acorn** <br>**European Fund**<sup>SM</sup> |
|  | **Year Ended** | **Year Ended** | **Year Ended** | **Year Ended** |
|  | **December 31, 2025**  | **December 31, 2025**  | **December 31, 2024**  | **December 31, 2024**  |
|  | **Shares** | **Dollars ($)** | **Shares** | **Dollars ($)** |
| **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** | **Capital stock activity** |
| Class A |  |  |  |  |
| Shares sold | 252907 | &nbsp;&nbsp;&nbsp;&nbsp; 6678105 | &nbsp;&nbsp;&nbsp;&nbsp; 194802 | &nbsp;&nbsp;&nbsp;&nbsp; 4856694 |
| Distributions reinvested | 176268 | &nbsp;&nbsp;&nbsp;&nbsp; 4179325 | &nbsp;&nbsp;&nbsp;&nbsp; 23930 | &nbsp;&nbsp;&nbsp;&nbsp; 597993 |
| Shares redeemed | (419898)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (10957037)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (445772)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (11331707)<br>|
| Net increase (decrease) | 9277 | &nbsp;&nbsp;&nbsp;&nbsp; (99607)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (227040)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (5877020)<br>|
| Advisor Class |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 25009 | &nbsp;&nbsp;&nbsp;&nbsp; 647374 |
| Distributions reinvested |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 580 | &nbsp;&nbsp;&nbsp;&nbsp; 15559 |
| Shares redeemed |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (97314)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (2474422)<br>|
| Net decrease |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (71725)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (1811489)<br>|
| Class C |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 106 | &nbsp;&nbsp;&nbsp;&nbsp; 2516 |
| Shares redeemed |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (72798)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (1709763)<br>|
| Net decrease |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (72692)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (1707247)<br>|
| Institutional Class |  |  |  |  |
| Shares sold | 57937 | &nbsp;&nbsp;&nbsp;&nbsp; 1557076 | &nbsp;&nbsp;&nbsp;&nbsp; 132787 | &nbsp;&nbsp;&nbsp;&nbsp; 3317734 |
| Distributions reinvested | 96347 | &nbsp;&nbsp;&nbsp;&nbsp; 2307505 | &nbsp;&nbsp;&nbsp;&nbsp; 19359 | &nbsp;&nbsp;&nbsp;&nbsp; 485098 |
| Shares redeemed | (378864)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (10018233)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (325949)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (8389451)<br>|
| Net decrease | (224580)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (6153652)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (173803)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4586619)<br>|
| Institutional 2 Class |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 3862 | &nbsp;&nbsp;&nbsp;&nbsp; 100981 |
| Shares redeemed |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (105850)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (2599932)<br>|
| Net decrease |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (101988)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (2498951)<br>|
| Institutional 3 Class |  |  |  |  |
| Shares sold |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 3 | &nbsp;&nbsp;&nbsp;&nbsp; 50 |
| Shares redeemed |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (1898)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (45780)<br>|
| Net decrease |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (1895)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (45730)<br>|
| **Total net decrease** | **(215303)**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **(6253259)**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **(649143)**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **(16527056)**<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights

Columbia Acorn<sup>®</sup> Fund

The following tables are intended to help you understand the Funds' financial performance. Certain information reflects financial results for a single share of a class held for the periods shown. Per share net investment income (loss) amounts are calculated based on average shares outstanding during the period. Total return assumes reinvestment of all dividends and distributions, if any. Total return does not reflect payment of sales charges, if any. Total return and portfolio turnover are not annualized for periods of less than one year. The ratios of expenses and net investment income are annualized for periods of less than one year. The portfolio turnover rate is calculated without regard to purchase and sales transactions of short-term instruments and certain derivatives, if any. If such transactions were included, a fund's portfolio turnover rate may be higher. A zero balance may reflect an amount rounding to less than $0.01 or 0.01%.

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | $8.55<br>| &nbsp;&nbsp; (0.05 )<sup>(c)</sup><br>| 0.44<br>| 0.39<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024 | $7.49<br>| &nbsp;&nbsp; (0.06) <br>| 1.12<br>| 1.06<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2023 | $6.16<br>| &nbsp;&nbsp; (0.03) <br>| 1.36<br>| 1.33<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $10.01<br>| &nbsp;&nbsp; (0.04) <br>| &nbsp;&nbsp; (3.34) <br>| &nbsp;&nbsp; (3.38) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.47) <br>| &nbsp;&nbsp; (0.47) <br>|
| Year Ended 12/31/2021 | $12.69<br>| &nbsp;&nbsp; (0.10) <br>| 1.07<br>| 0.97<br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (3.51) <br>| &nbsp;&nbsp; (3.65) <br>|
| **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** |
| Year Ended 12/31/2025 | $11.77<br>| &nbsp;&nbsp; (0.16 )<sup>(c)</sup><br>| 0.61<br>| 0.45<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024 | $10.39<br>| &nbsp;&nbsp; (0.17) <br>| 1.55<br>| 1.38<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2023 | $8.61<br>| &nbsp;&nbsp; (0.11) <br>| 1.89<br>| 1.78<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $13.72<br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (4.57) <br>| &nbsp;&nbsp; (4.70) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.41) <br>| &nbsp;&nbsp; (0.41) <br>|
| Year Ended 12/31/2021 | $16.14<br>| &nbsp;&nbsp; (0.26) <br>| 1.40<br>| 1.14<br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (3.43) <br>| &nbsp;&nbsp; (3.56) <br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | $12.51<br>| &nbsp;&nbsp; (0.05 )<sup>(c)</sup><br>| 0.65<br>| 0.60<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024 | $10.93<br>| &nbsp;&nbsp; (0.06) <br>| 1.64<br>| 1.58<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2023 | $8.97<br>| &nbsp;&nbsp; (0.02) <br>| 1.98<br>| 1.96<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $14.22<br>| &nbsp;&nbsp; (0.03) <br>| &nbsp;&nbsp; (4.75) <br>| &nbsp;&nbsp; (4.78) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.47) <br>| &nbsp;&nbsp; (0.47) <br>|
| Year Ended 12/31/2021 | $16.60<br>| &nbsp;&nbsp; (0.09) <br>| 1.43<br>| 1.34<br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (3.59) <br>| &nbsp;&nbsp; (3.72) <br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | $13.81<br>| &nbsp;&nbsp; (0.05 )<sup>(c)</sup><br>| 0.72<br>| 0.67<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024 | $12.06<br>| &nbsp;&nbsp; (0.06) <br>| 1.81<br>| 1.75<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2023 | $9.89<br>| &nbsp;&nbsp; (0.02) <br>| 2.19<br>| 2.17<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $15.62<br>| &nbsp;&nbsp; (0.03) <br>| &nbsp;&nbsp; (5.23) <br>| &nbsp;&nbsp; (5.26) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.47) <br>| &nbsp;&nbsp; (0.47) <br>|
| Year Ended 12/31/2021 | $17.88<br>| &nbsp;&nbsp; (0.10) <br>| 1.57<br>| 1.47<br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (3.60) <br>| &nbsp;&nbsp; (3.73) <br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | $14.06<br>| &nbsp;&nbsp; (0.04 )<sup>(c)</sup><br>| 0.73<br>| 0.69<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024 | $12.28<br>| &nbsp;&nbsp; (0.05) <br>| 1.83<br>| 1.78<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2023 | $10.07<br>| &nbsp;&nbsp; (0.02) <br>| 2.23<br>| 2.21<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $15.88<br>| &nbsp;&nbsp; (0.02) <br>| &nbsp;&nbsp; (5.32) <br>| &nbsp;&nbsp; (5.34) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.47) <br>| &nbsp;&nbsp; (0.47) <br>|
| Year Ended 12/31/2021 | $18.12<br>| &nbsp;&nbsp; (0.09) <br>| 1.60<br>| 1.51<br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (3.61) <br>| &nbsp;&nbsp; (3.75) <br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn<sup>®</sup> Fund

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total gross** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total net** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a),(b)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $8.94<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.56%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.09%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.07% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.62% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $475068<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $8.55<br>| &nbsp;&nbsp;&nbsp;&nbsp; 14.15% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.16%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.74%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $544609<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $7.49<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.59% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.15%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.46%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $570240<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $6.16<br>| &nbsp;&nbsp;&nbsp;&nbsp; (34.01%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08% <br><sup>(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.53%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $521243<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $10.01<br>| &nbsp;&nbsp;&nbsp;&nbsp; 8.79%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.08% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.80%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $919643<br>|
| **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $12.22<br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.82%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.82% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (1.37% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $5069<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $11.77<br>| &nbsp;&nbsp;&nbsp;&nbsp; 13.28% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.91%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (1.49%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $7263<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $10.39<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.67% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.90%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (1.21%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $8991<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $8.61<br>| &nbsp;&nbsp;&nbsp;&nbsp; (34.48%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83% <br><sup>(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (1.29%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $9153<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $13.72<br>| &nbsp;&nbsp;&nbsp;&nbsp; 7.95%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (1.54%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $24546<br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $13.11<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.80%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.82% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.37% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $1604235<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $12.51<br>| &nbsp;&nbsp;&nbsp;&nbsp; 14.46% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.91%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.49%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $1767918<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $10.93<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.85% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.90%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.21%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $2110299<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $8.97<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.78%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83% <br><sup>(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.28%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $1865518<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $14.22<br>| &nbsp;&nbsp;&nbsp;&nbsp; 8.99%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.55%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $3413006<br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $14.48<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.85%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.34% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $25586<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $13.81<br>| &nbsp;&nbsp;&nbsp;&nbsp; 14.51% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.89%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.80%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.46%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $27386<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $12.06<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.94% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.87%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.18%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $28765<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $9.89<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.83% )<sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.81% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.80% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.26%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $23445<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $15.62<br>| &nbsp;&nbsp;&nbsp;&nbsp; 9.09% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.80%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.80%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.52%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $52797<br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $14.75<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.91%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.76%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.74%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.29% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $23301<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $14.06<br>| &nbsp;&nbsp;&nbsp;&nbsp; 14.50% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.41%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $29552<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $12.28<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.95% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.76%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.17%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $28181<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $10.07<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.77%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.77% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.77% <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.23%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $47945<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $15.88<br>| &nbsp;&nbsp;&nbsp;&nbsp; 9.16%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.46%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $78955<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn<sup>®</sup> Fund

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | $12.51<br>| &nbsp;&nbsp; (0.05 )<sup>(c)</sup><br>| 0.66<br>| 0.61<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2024<sup>(g)</sup> <br>| $12.23<br>| &nbsp;&nbsp; (0.01) <br>| 0.29<br>| 0.28<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| **Notes to Financial Highlights**  | **Notes to Financial Highlights**  |
| (a) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund's reported expense ratios. |
| (b) | Total net expenses include the impact of certain fee waivers/expense reimbursements made by the Investment Manager and certain of its affiliates, if applicable.  |
| (c) | Includes income resulting from European Union tax reclaims, net of an IRS closing agreement for European Union tax reclaims, if applicable. The effect of these amounted to: |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Class** | **Net Investment income per share ($)** | **Net Investment income ratio (%)** |
| **Year Ended 12/31/2025** |  |  |
| Class A | lessthan<br> 0.01<br>| 0.05 |
| Class C | 0.01 | 0.05 |
| Institutional Class | 0.01 | 0.05 |
| Institutional 2 Class | 0.01 | 0.05 |
| Institutional 3 Class | 0.01 | 0.05 |
| Class S | 0.01 | 0.05 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(d) The benefits derived from expense reductions had an impact of less than 0.01%.

&nbsp;&nbsp;&nbsp;&nbsp;(e) Had the Investment Manager and/or Transfer Agent not waived fees and/or reimbursed a portion of expenses, total return would have been reduced.

&nbsp;&nbsp;&nbsp;&nbsp;(f) Ratios include Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations. If these had been excluded, expenses would have been higher by 0.03%.

&nbsp;&nbsp;&nbsp;&nbsp;(g) Class S shares commenced operations on October 2, 2024. Per share data and total return reflect activity from that date.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn<sup>®</sup> Fund

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total gross** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total net** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a),(b)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $13.12<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.82% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.37% )<sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $302602<br>|
|  Year Ended 12/31/2024 <br><sup>(g)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; $12.51<br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.29% <br><sup>(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.95%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.83%<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.41%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $352105<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights

Columbia Acorn International<sup>®</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | $21.54<br>| 0.25 <br><sup>(c)</sup><br>| 2.35<br>| 2.60<br>| &nbsp;&nbsp; (0.30) <br>| &nbsp;&nbsp; (1.00) <br>| &nbsp;&nbsp; (1.30) <br>|
| Year Ended 12/31/2024 | $25.46<br>| 0.18 <br><sup>(c)</sup><br>| &nbsp;&nbsp; (1.41) <br>| &nbsp;&nbsp; (1.23) <br>| &nbsp;&nbsp; (0.71) <br>| &nbsp;&nbsp; (1.98) <br>| &nbsp;&nbsp; (2.69) <br>|
| Year Ended 12/31/2023 | $21.34<br>| 0.09<br>| 4.03<br>| 4.12<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $33.19<br>| 0.17 <br><sup>(g)</sup><br>| &nbsp;&nbsp; (11.35) <br>| &nbsp;&nbsp; (11.18) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.67) <br>| &nbsp;&nbsp; (0.67) <br>|
| Year Ended 12/31/2021 | $34.31<br>| 0.01<br>| 4.08<br>| 4.09<br>| &nbsp;&nbsp; (0.38) <br>| &nbsp;&nbsp; (4.83) <br>| &nbsp;&nbsp; (5.21) <br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | $21.68<br>| 0.31 <br><sup>(c)</sup><br>| 2.36<br>| 2.67<br>| &nbsp;&nbsp; (0.36) <br>| &nbsp;&nbsp; (1.00) <br>| &nbsp;&nbsp; (1.36) <br>|
| Year Ended 12/31/2024 | $25.66<br>| 0.26 <br><sup>(c)</sup><br>| &nbsp;&nbsp; (1.43) <br>| &nbsp;&nbsp; (1.17) <br>| &nbsp;&nbsp; (0.83) <br>| &nbsp;&nbsp; (1.98) <br>| &nbsp;&nbsp; (2.81) <br>|
| Year Ended 12/31/2023 | $21.46<br>| 0.15<br>| 4.05<br>| 4.20<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $33.28<br>| 0.23 <br><sup>(g)</sup><br>| &nbsp;&nbsp; (11.38) <br>| &nbsp;&nbsp; (11.15) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.67) <br>| &nbsp;&nbsp; (0.67) <br>|
| Year Ended 12/31/2021 | $34.47<br>| 0.10<br>| 4.09<br>| 4.19<br>| &nbsp;&nbsp; (0.55) <br>| &nbsp;&nbsp; (4.83) <br>| &nbsp;&nbsp; (5.38) <br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | $21.66<br>| 0.32 <br><sup>(c)</sup><br>| 2.37<br>| 2.69<br>| &nbsp;&nbsp; (0.38) <br>| &nbsp;&nbsp; (1.00) <br>| &nbsp;&nbsp; (1.38) <br>|
| Year Ended 12/31/2024 | $25.66<br>| 0.26 <br><sup>(c)</sup><br>| &nbsp;&nbsp; (1.42) <br>| &nbsp;&nbsp; (1.16) <br>| &nbsp;&nbsp; (0.86) <br>| &nbsp;&nbsp; (1.98) <br>| &nbsp;&nbsp; (2.84) <br>|
| Year Ended 12/31/2023 | $21.45<br>| 0.17<br>| 4.04<br>| 4.21<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $33.25<br>| 0.24 <br><sup>(g)</sup><br>| &nbsp;&nbsp; (11.37) <br>| &nbsp;&nbsp; (11.13) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.67) <br>| &nbsp;&nbsp; (0.67) <br>|
| Year Ended 12/31/2021 | $34.46<br>| 0.12<br>| 4.09<br>| 4.21<br>| &nbsp;&nbsp; (0.59) <br>| &nbsp;&nbsp; (4.83) <br>| &nbsp;&nbsp; (5.42) <br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | $22.12<br>| 0.34 <br><sup>(c)</sup><br>| 2.41<br>| 2.75<br>| &nbsp;&nbsp; (0.39) <br>| &nbsp;&nbsp; (1.00) <br>| &nbsp;&nbsp; (1.39) <br>|
| Year Ended 12/31/2024 | $26.15<br>| 0.28 <br><sup>(c)</sup><br>| &nbsp;&nbsp; (1.45) <br>| &nbsp;&nbsp; (1.17) <br>| &nbsp;&nbsp; (0.88) <br>| &nbsp;&nbsp; (1.98) <br>| &nbsp;&nbsp; (2.86) <br>|
| Year Ended 12/31/2023 | $21.84<br>| 0.18<br>| 4.13<br>| 4.31<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $33.83<br>| 0.26 <br><sup>(g)</sup><br>| &nbsp;&nbsp; (11.58) <br>| &nbsp;&nbsp; (11.32) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.67) <br>| &nbsp;&nbsp; (0.67) <br>|
| Year Ended 12/31/2021 | $34.99<br>| 0.15<br>| 4.14<br>| 4.29<br>| &nbsp;&nbsp; (0.62) <br>| &nbsp;&nbsp; (4.83) <br>| &nbsp;&nbsp; (5.45) <br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International<sup>®</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $22.84<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.12%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.30% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.21% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.06% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $115158<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $21.54<br>| &nbsp;&nbsp;&nbsp;&nbsp; (5.09%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.38% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.22% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.73% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $123302<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.46<br>| &nbsp;&nbsp;&nbsp;&nbsp; 19.31%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.37% <br><sup>(d),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(d),(e),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.41%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $155877<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.34<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.81%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.27% <br><sup>(d),(f),(h)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.23% <br><sup>(d),(e),(f),(h)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.71%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 29%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $151725<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.19<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.63%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.23% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.03%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $282125<br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $22.99<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.36%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.05% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.96% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.31% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $515251<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $21.68<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4.82%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.13% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.97% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.01% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $525326<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.66<br>| &nbsp;&nbsp;&nbsp;&nbsp; 19.57%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.12% <br><sup>(d),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.99% <br><sup>(d),(e),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.66%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $837217<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.46<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.63%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.03% <br><sup>(d),(f),(h)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.98% <br><sup>(d),(e),(f),(h)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.96%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 29%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $906415<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.28<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.89%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.99% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.98% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $1727042<br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $22.97<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.44%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.00% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.90% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.37% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $17028<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $21.66<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4.79%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.09% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.92% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.03% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $16507<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.66<br>| &nbsp;&nbsp;&nbsp;&nbsp; 19.63%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.05% <br><sup>(d),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.92% <br><sup>(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.75%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $22937<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.45<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.60%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.97% <br><sup>(d),(f),(h)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.92% <br><sup>(d),(f),(h)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.04%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 29%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $80059<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.25<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.97%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.95% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.92% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.34%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $126973<br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $23.48<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.46%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.93% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.85% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.43% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $63201<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $22.12<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4.75%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.03% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.88% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.07% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $108049<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $26.15<br>| &nbsp;&nbsp;&nbsp;&nbsp; 19.73%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.01% <br><sup>(d),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.89% <br><sup>(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.77%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $131038<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.84<br>| &nbsp;&nbsp;&nbsp;&nbsp; (33.58%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.92% <br><sup>(d),(f),(h)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.88% <br><sup>(d),(f),(h)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.10%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 29%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $133738<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.83<br>| &nbsp;&nbsp;&nbsp;&nbsp; 13.00%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.90% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.88% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.40%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $179991<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International<sup>®</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | $21.68<br>0.31 <br><sup>(c)</sup><br>| 2.36<br>| 2.67<br>| &nbsp;&nbsp; (0.36) <br>| &nbsp;&nbsp; (1.00) <br>| &nbsp;&nbsp; (1.36) <br>|
| Year Ended 12/31/2024<sup>(i)</sup> <br>| $26.68<br>0.00 <br><sup>(c)</sup><br>| &nbsp;&nbsp; (3.14) <br>| &nbsp;&nbsp; (3.14) <br>| &nbsp;&nbsp; (0.31) <br>| &nbsp;&nbsp; (1.55) <br>| &nbsp;&nbsp; (1.86) <br>|

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| **Notes to Financial Highlights**  | **Notes to Financial Highlights**  |
| (a) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund's reported expense ratios. |
| (b) | Total net expenses include the impact of certain fee waivers/expense reimbursements made by the Investment Manager and certain of its affiliates, if applicable.  |
| (c) | Includes income resulting from European Union tax reclaims, net of an IRS closing agreement for European Union tax reclaims, if applicable. The effect of these amounted to: |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Class** | **Net Investment income per share ($)** | **Net Investment income ratio (%)** |
| **Year Ended 12/31/2025** |  |  |
| Class A | 0.08 | 0.32 |
| Institutional Class | 0.07 | 0.32 |
| Institutional 2 Class | 0.07 | 0.32 |
| Institutional 3 Class | 0.08 | 0.36 |
| Class S | 0.08 | 0.33 |
| **Year Ended 12/31/2024** |  |  |
| Class A | 0.04 | 0.17 |
| Institutional Class | 0.04 | 0.17 |
| Institutional 2 Class | 0.04 | 0.17 |
| Institutional 3 Class | 0.04 | 0.17 |
| Class S | 0.01 | 0.17 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(d) Ratios include line of credit interest expense. For the periods indicated below, if line of credit interest expense had been excluded, expenses would have been lower by:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
| **Class** | **12/31/2025** | **12/31/2024** | **12/31/2023** | **12/31/2022** | **12/31/2021** |
| Class A | less than 0.01% | less than 0.01% | &nbsp;&nbsp; 0.01% | less than 0.01% | &nbsp;&nbsp; —% |
| Institutional Class | less than 0.01% | less than 0.01% | &nbsp;&nbsp; 0.01% | less than 0.01% | &nbsp;&nbsp; —% |
| Institutional 2 Class | less than 0.01% | less than 0.01% | less than 0.01% | less than 0.01% | &nbsp;&nbsp; —% |
| Institutional 3 Class | less than 0.01% | less than 0.01% | &nbsp;&nbsp; 0.01% | less than 0.01% | &nbsp;&nbsp; —% |
| Class S | less than 0.01% | less than 0.01% | &nbsp;&nbsp; —% | &nbsp;&nbsp; —% | &nbsp;&nbsp; —% |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(e) The benefits derived from expense reductions had an impact of less than 0.01%.

&nbsp;&nbsp;&nbsp;&nbsp;(f) Ratios include interest on collateral expense which is less than 0.01%.

&nbsp;&nbsp;&nbsp;&nbsp;(g) Net investment income per share includes European Union tax reclaims. The effect of these reclaims amounted to $0.02 per share.

&nbsp;&nbsp;&nbsp;&nbsp;(h) Ratios include Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations. If these had been excluded, expenses would have been higher by 0.03%.

&nbsp;&nbsp;&nbsp;&nbsp;(i) Class S shares commenced operations on October 2, 2024. Per share data and total return reflect activity from that date.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International<sup>®</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $22.99<br>| &nbsp;&nbsp;&nbsp;&nbsp; 12.36%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.05% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.96% <br><sup>(d),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.31% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $95259<br>|
|  Year Ended 12/31/2024 <br><sup>(i)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; $21.68<br>| &nbsp;&nbsp;&nbsp;&nbsp; (11.76%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.20% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.97% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.08% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 28%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $111119<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights

Columbia Acorn International Select<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | $25.18<br>| 0.66 <br><sup>(c)</sup><br>| 4.38<br>| 5.04<br>| &nbsp;&nbsp; (1.67) <br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (1.80) <br>|
| Year Ended 12/31/2024 | $25.48<br>| 0.23<br>| &nbsp;&nbsp; (0.29) <br>| &nbsp;&nbsp; (0.06) <br>| &nbsp;&nbsp; (0.24) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.24) <br>|
| Year Ended 12/31/2023 | $21.57<br>| 0.07<br>| 3.84<br>| 3.91<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $35.43<br>| 0.12 <br><sup>(f)</sup><br>| &nbsp;&nbsp; (13.06) <br>| &nbsp;&nbsp; (12.94) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.92) <br>| &nbsp;&nbsp; (0.92) <br>|
| Year Ended 12/31/2021 | $33.67<br>| &nbsp;&nbsp; (0.05) <br>| 3.50<br>| 3.45<br>| &nbsp;&nbsp; (0.28) <br>| &nbsp;&nbsp; (1.41) <br>| &nbsp;&nbsp; (1.69) <br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | $25.75<br>| 0.74 <br><sup>(c)</sup><br>| 4.49<br>| 5.23<br>| &nbsp;&nbsp; (1.81) <br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (1.94) <br>|
| Year Ended 12/31/2024 | $26.04<br>| 0.31<br>| &nbsp;&nbsp; (0.30) <br>| 0.01<br>| &nbsp;&nbsp; (0.30) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.30) <br>|
| Year Ended 12/31/2023 | $21.99<br>| 0.13<br>| 3.92<br>| 4.05<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $36.01<br>| 0.18 <br><sup>(f)</sup><br>| &nbsp;&nbsp; (13.28) <br>| &nbsp;&nbsp; (13.10) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.92) <br>| &nbsp;&nbsp; (0.92) <br>|
| Year Ended 12/31/2021 | $34.25<br>| 0.04<br>| 3.56<br>| 3.60<br>| &nbsp;&nbsp; (0.43) <br>| &nbsp;&nbsp; (1.41) <br>| &nbsp;&nbsp; (1.84) <br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | $26.07<br>| 0.79 <br><sup>(c)</sup><br>| 4.53<br>| 5.32<br>| &nbsp;&nbsp; (1.88) <br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (2.01) <br>|
| Year Ended 12/31/2024 | $26.34<br>| 0.34<br>| &nbsp;&nbsp; (0.28) <br>| 0.06<br>| &nbsp;&nbsp; (0.33) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.33) <br>|
| Year Ended 12/31/2023 | $22.22<br>| 0.15<br>| 3.97<br>| 4.12<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $36.33<br>| 0.20 <br><sup>(f)</sup><br>| &nbsp;&nbsp; (13.39) <br>| &nbsp;&nbsp; (13.19) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.92) <br>| &nbsp;&nbsp; (0.92) <br>|
| Year Ended 12/31/2021 | $34.57<br>| 0.06<br>| 3.60<br>| 3.66<br>| &nbsp;&nbsp; (0.49) <br>| &nbsp;&nbsp; (1.41) <br>| &nbsp;&nbsp; (1.90) <br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | $26.07<br>| 0.79 <br><sup>(c)</sup><br>| 4.55<br>| 5.34<br>| &nbsp;&nbsp; (1.91) <br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (2.04) <br>|
| Year Ended 12/31/2024 | $26.35<br>| 0.35<br>| &nbsp;&nbsp; (0.29) <br>| 0.06<br>| &nbsp;&nbsp; (0.34) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.34) <br>|
| Year Ended 12/31/2023 | $22.21<br>| 0.17<br>| 3.97<br>| 4.14<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2022 | $36.31<br>| 0.21 <br><sup>(f)</sup><br>| &nbsp;&nbsp; (13.39) <br>| &nbsp;&nbsp; (13.18) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.92) <br>| &nbsp;&nbsp; (0.92) <br>|
| Year Ended 12/31/2021 | $34.56<br>| 0.09<br>| 3.59<br>| 3.68<br>| &nbsp;&nbsp; (0.52) <br>| &nbsp;&nbsp; (1.41) <br>| &nbsp;&nbsp; (1.93) <br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International Select<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $28.42<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.31%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.47% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.12% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.39% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $116233<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $25.18<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.30%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.55% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.23% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.86%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 69%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $110629<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.48<br>| &nbsp;&nbsp;&nbsp;&nbsp; 18.13%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.55% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.23% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.30%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 43%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $128076<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.57<br>| &nbsp;&nbsp;&nbsp;&nbsp; (36.80%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.50% <br><sup>(d),(g)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(d),(e),(g)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.48%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $124963<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $35.43<br>| &nbsp;&nbsp;&nbsp;&nbsp; 10.49%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.44% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.23% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.15%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $235103<br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $29.04<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.61%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.22% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.87% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.63% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $58415<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $25.75<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.04%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.29% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.98% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.14%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 69%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $54447<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $26.04<br>| &nbsp;&nbsp;&nbsp;&nbsp; 18.42%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.30% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.98% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.55%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 43%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $79765<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $21.99<br>| &nbsp;&nbsp;&nbsp;&nbsp; (36.65%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.25% <br><sup>(d),(g)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.99% <br><sup>(d),(e),(g)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.73%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $79829<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $36.01<br>| &nbsp;&nbsp;&nbsp;&nbsp; 10.79%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.19% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.98% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.10%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $159876<br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $29.38<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.73%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.09% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.74% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.76% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $3185<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $26.07<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.14%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.16% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.84% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 69%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $3963<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $26.34<br>| &nbsp;&nbsp;&nbsp;&nbsp; 18.54%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.16% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.86% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.64%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 43%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $5810<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $22.22<br>| &nbsp;&nbsp;&nbsp;&nbsp; (36.57%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.11% <br><sup>(d),(g)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.89% <br><sup>(d),(g)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.78%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $9225<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $36.33<br>| &nbsp;&nbsp;&nbsp;&nbsp; 10.87%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.10% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.89% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.17%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $51805<br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $29.37<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.81%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.04% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.69% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.78% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $9382<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $26.07<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.14%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.11% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.79% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.31%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 69%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $8631<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $26.35<br>| &nbsp;&nbsp;&nbsp;&nbsp; 18.64%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.11% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.81% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.70%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 43%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $9404<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $22.21<br>| &nbsp;&nbsp;&nbsp;&nbsp; (36.56%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.06% <br><sup>(d),(g)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.84% <br><sup>(d),(g)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.81%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $11188<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $36.31<br>| &nbsp;&nbsp;&nbsp;&nbsp; 10.93%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.05% <br><sup>(d)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.84% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.24%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 27%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $28694<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International Select<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | $25.75<br>| 0.74 <br><sup>(c)</sup><br>| 4.49<br>| 5.23<br>| &nbsp;&nbsp; (1.81) <br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; (1.94) <br>|
| Year Ended 12/31/2024<sup>(h)</sup> <br>| $27.97<br>| 0.03<br>| &nbsp;&nbsp; (2.25) <br>| &nbsp;&nbsp; (2.22) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| **Notes to Financial Highlights**  | **Notes to Financial Highlights**  |
| (a) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund's reported expense ratios. |
| (b) | Total net expenses include the impact of certain fee waivers/expense reimbursements made by the Investment Manager and certain of its affiliates, if applicable.  |
| (c) | Includes income resulting from European Union tax reclaims, net of an IRS closing agreement for European Union tax reclaims, if applicable. The effect of these amounted to: |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | |
|:---|:---|:---|
| **Class** | **Net Investment income per share ($)** | **Net Investment income ratio (%)** |
| **Year Ended 12/31/2025** |  |  |
| Class A | 0.37 | 1.33 |
| Institutional Class | 0.37 | 1.32 |
| Institutional 2 Class | 0.40 | 1.39 |
| Institutional 3 Class | 0.37 | 1.30 |
| Class S | 0.37 | 1.33 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(d) Ratios include line of credit interest expense which is less than 0.01%.

&nbsp;&nbsp;&nbsp;&nbsp;(e) The benefits derived from expense reductions had an impact of less than 0.01%.

&nbsp;&nbsp;&nbsp;&nbsp;(f) Net investment income per share includes European Union tax reclaims. The effect of these reclaims amounted to $0.02 per share.

&nbsp;&nbsp;&nbsp;&nbsp;(g) Ratios include Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations. If these had been excluded, expenses would have been higher by 0.02%.

&nbsp;&nbsp;&nbsp;&nbsp;(h) Class S shares commenced operations on October 2, 2024. Per share data and total return reflect activity from that date.

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn International Select<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total gross** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total net** <br>**expense** <br>**ratio to** <br>**average** <br>**net assets**<sup>(a),(b)</sup> <br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $29.04<br>| &nbsp;&nbsp;&nbsp;&nbsp; 20.61%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.22% <br><sup>(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.87% <br><sup>(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.64% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $12625<br>|
|  Year Ended 12/31/2024 <br><sup>(h)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; $25.75<br>| &nbsp;&nbsp;&nbsp;&nbsp; (7.94%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.38%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.98%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.47%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 69%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $11956<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights

Columbia Thermostat Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | $16.28<br>| 0.49<br>| 1.90<br>| 2.39<br>| &nbsp;&nbsp; (0.55) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.55) <br>|
| Year Ended 12/31/2024 | $15.61<br>| 0.46<br>| 0.74<br>| 1.20<br>| &nbsp;&nbsp; (0.53) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.53) <br>|
| Year Ended 12/31/2023 | $14.36<br>| 0.39<br>| 1.24<br>| 1.63<br>| &nbsp;&nbsp; (0.38) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.38) <br>|
| Year Ended 12/31/2022 | $17.01<br>| 0.26<br>| &nbsp;&nbsp; (2.49) <br>| &nbsp;&nbsp; (2.23) <br>| &nbsp;&nbsp; (0.28) <br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (0.42) <br>|
| Year Ended 12/31/2021 | $18.31<br>| 0.24<br>| 0.89<br>| 1.13<br>| &nbsp;&nbsp; (0.26) <br>| &nbsp;&nbsp; (2.17) <br>| &nbsp;&nbsp; (2.43) <br>|
| **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** |
| Year Ended 12/31/2025 | $16.40<br>| 0.36<br>| 1.91<br>| 2.27<br>| &nbsp;&nbsp; (0.43) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.43) <br>|
| Year Ended 12/31/2024 | $15.73<br>| 0.34<br>| 0.74<br>| 1.08<br>| &nbsp;&nbsp; (0.41) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.41) <br>|
| Year Ended 12/31/2023 | $14.48<br>| 0.27<br>| 1.25<br>| 1.52<br>| &nbsp;&nbsp; (0.27) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.27) <br>|
| Year Ended 12/31/2022 | $17.14<br>| 0.14<br>| &nbsp;&nbsp; (2.49) <br>| &nbsp;&nbsp; (2.35) <br>| &nbsp;&nbsp; (0.17) <br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (0.31) <br>|
| Year Ended 12/31/2021 | $18.43<br>| 0.09<br>| 0.90<br>| 0.99<br>| &nbsp;&nbsp; (0.11) <br>| &nbsp;&nbsp; (2.17) <br>| &nbsp;&nbsp; (2.28) <br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | $15.95<br>| 0.53<br>| 1.86<br>| 2.39<br>| &nbsp;&nbsp; (0.60) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.60) <br>|
| Year Ended 12/31/2024 | $15.30<br>| 0.50<br>| 0.72<br>| 1.22<br>| &nbsp;&nbsp; (0.57) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.57) <br>|
| Year Ended 12/31/2023 | $14.08<br>| 0.42<br>| 1.22<br>| 1.64<br>| &nbsp;&nbsp; (0.42) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.42) <br>|
| Year Ended 12/31/2022 | $16.69<br>| 0.29<br>| &nbsp;&nbsp; (2.44) <br>| &nbsp;&nbsp; (2.15) <br>| &nbsp;&nbsp; (0.32) <br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (0.46) <br>|
| Year Ended 12/31/2021 | $18.01<br>| 0.28<br>| 0.87<br>| 1.15<br>| &nbsp;&nbsp; (0.30) <br>| &nbsp;&nbsp; (2.17) <br>| &nbsp;&nbsp; (2.47) <br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | $16.10<br>| 0.55<br>| 1.88<br>| 2.43<br>| &nbsp;&nbsp; (0.61) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.61) <br>|
| Year Ended 12/31/2024 | $15.44<br>| 0.50<br>| 0.73<br>| 1.23<br>| &nbsp;&nbsp; (0.57) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.57) <br>|
| Year Ended 12/31/2023 | $14.21<br>| 0.43<br>| 1.22<br>| 1.65<br>| &nbsp;&nbsp; (0.42) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.42) <br>|
| Year Ended 12/31/2022 | $16.84<br>| 0.29<br>| &nbsp;&nbsp; (2.45) <br>| &nbsp;&nbsp; (2.16) <br>| &nbsp;&nbsp; (0.33) <br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (0.47) <br>|
| Year Ended 12/31/2021 | $18.14<br>| 0.29<br>| 0.89<br>| 1.18<br>| &nbsp;&nbsp; (0.31) <br>| &nbsp;&nbsp; (2.17) <br>| &nbsp;&nbsp; (2.48) <br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | $16.06<br>| 0.56<br>| 1.87<br>| 2.43<br>| &nbsp;&nbsp; (0.61) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.61) <br>|
| Year Ended 12/31/2024 | $15.41<br>| 0.51<br>| 0.72<br>| 1.23<br>| &nbsp;&nbsp; (0.58) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.58) <br>|
| Year Ended 12/31/2023 | $14.18<br>| 0.44<br>| 1.22<br>| 1.66<br>| &nbsp;&nbsp; (0.43) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.43) <br>|
| Year Ended 12/31/2022 | $16.80<br>| 0.31<br>| &nbsp;&nbsp; (2.45) <br>| &nbsp;&nbsp; (2.14) <br>| &nbsp;&nbsp; (0.34) <br>| &nbsp;&nbsp; (0.14) <br>| &nbsp;&nbsp; (0.48) <br>|
| Year Ended 12/31/2021 | $18.11<br>| 0.36<br>| 0.82<br>| 1.18<br>| &nbsp;&nbsp; (0.32) <br>| &nbsp;&nbsp; (2.17) <br>| &nbsp;&nbsp; (2.49) <br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Thermostat Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $18.12<br>| &nbsp;&nbsp;&nbsp;&nbsp; 14.75%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.49% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.49% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.82%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $390531<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $16.28<br>| &nbsp;&nbsp;&nbsp;&nbsp; 7.68%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.56% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.50% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.83%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $385771<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $15.61<br>| &nbsp;&nbsp;&nbsp;&nbsp; 11.38%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.57% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.49% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.59%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 148%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $428092<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $14.36<br>| &nbsp;&nbsp;&nbsp;&nbsp; (13.14%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.54% <br><sup>(c),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.50% <br><sup>(c),(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.70%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $450566<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $17.01<br>| &nbsp;&nbsp;&nbsp;&nbsp; 6.16%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.54% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.50% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.26%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 49%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $624373<br>|
| **Class C** | **Class C** | **Class C** | **Class C** | **Class C** | **Class C** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $18.24<br>| &nbsp;&nbsp;&nbsp;&nbsp; 13.86%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.06%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $82776<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $16.40<br>| &nbsp;&nbsp;&nbsp;&nbsp; 6.86%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.31% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.25% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.07%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $87900<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $15.73<br>| &nbsp;&nbsp;&nbsp;&nbsp; 10.52%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.32% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.24% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.82%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 148%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $111123<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $14.48<br>| &nbsp;&nbsp;&nbsp;&nbsp; (13.75%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.29% <br><sup>(c),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.25% <br><sup>(c),(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.93%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $126802<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $17.14<br>| &nbsp;&nbsp;&nbsp;&nbsp; 5.40%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.29% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.25% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.48%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 49%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $189990<br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $17.74<br>| &nbsp;&nbsp;&nbsp;&nbsp; 15.02%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.09%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $702762<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $15.95<br>| &nbsp;&nbsp;&nbsp;&nbsp; 7.97%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.31% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.12%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $624613<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $15.30<br>| &nbsp;&nbsp;&nbsp;&nbsp; 11.66%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.32% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.85%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 148%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $636587<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $14.08<br>| &nbsp;&nbsp;&nbsp;&nbsp; (12.92%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.29% <br><sup>(c),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c),(d),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.93%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $600671<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $16.69<br>| &nbsp;&nbsp;&nbsp;&nbsp; 6.42%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.29% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.52%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 49%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $902841<br>|
| **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** | **Institutional 2 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $17.92<br>| &nbsp;&nbsp;&nbsp;&nbsp; 15.12%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.20% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.15%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $92061<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $16.10<br>| &nbsp;&nbsp;&nbsp;&nbsp; 8.01%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.27% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.20% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.11%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $76935<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $15.44<br>| &nbsp;&nbsp;&nbsp;&nbsp; 11.67%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.28% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.20% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 148%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $86925<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $14.21<br>| &nbsp;&nbsp;&nbsp;&nbsp; (12.88%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.20% <br><sup>(c),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.94%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $90290<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $16.84<br>| &nbsp;&nbsp;&nbsp;&nbsp; 6.53%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.20% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.53%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 49%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $169246<br>|
| **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** | **Institutional 3 Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $17.88<br>| &nbsp;&nbsp;&nbsp;&nbsp; 15.20%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.15% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $15711<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $16.06<br>| &nbsp;&nbsp;&nbsp;&nbsp; 8.00%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.23% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.16% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.18%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $10613<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $15.41<br>| &nbsp;&nbsp;&nbsp;&nbsp; 11.73%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.16% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.96%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 148%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $11038<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $14.18<br>| &nbsp;&nbsp;&nbsp;&nbsp; (12.82%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.21% <br><sup>(c),(e)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.16% <br><sup>(c),(e)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 2.04%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 88%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $10184<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $16.80<br>| &nbsp;&nbsp;&nbsp;&nbsp; 6.52%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.21% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.17% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.94%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 49%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $15581<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Thermostat Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | $15.95<br>| 0.53<br>| 1.86<br>| 2.39<br>| &nbsp;&nbsp; (0.60) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.60) <br>|
| Year Ended 12/31/2024<sup>(f)</sup> <br>| $16.61<br>| 0.17<br>| &nbsp;&nbsp; (0.33 )<sup>(g)</sup><br>| &nbsp;&nbsp; (0.16) <br>| &nbsp;&nbsp; (0.50) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.50) <br>|

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| **Notes to Financial Highlights**  | **Notes to Financial Highlights**  |
| (a) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund's reported expense ratios. |
| (b) | Total net expenses include the impact of certain fee waivers/expense reimbursements made by the Investment Manager and certain of its affiliates, if applicable.  |
| (c) | Ratios include line of credit interest expense which is less than 0.01%.  |
| (d) | The benefits derived from expense reductions had an impact of less than 0.01%. |
| (e) | Ratios include Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations. If these had been excluded, expenses would have been higher by 0.01%.  |
| (f) | Class S shares commenced operations on October 2, 2024. Per share data and total return reflect activity from that date. |
| (g) | Calculation of the net gain (loss) per share (both realized and unrealized) does not correlate to the aggregate realized and unrealized gain (loss) presented in the Statement of Operations due to timing of Fund shares sold and redeemed in relation to fluctuations in the market value of the portfolio. For a new share class, the difference may be due to the timing of the commencement of operations for the share class. |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Thermostat Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class S** | **Class S** | **Class S** | **Class S** | **Class S** | **Class S** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $17.74<br>| &nbsp;&nbsp;&nbsp;&nbsp; 15.02%<br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.24% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 3.08%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 84%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $12805<br>|
|  Year Ended 12/31/2024 <br><sup>(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; $15.95<br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.95%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 0.34% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 0.25% <br><sup>(c)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 4.44%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 114%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $12794<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights

Columbia Acorn European Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Net asset value,** <br>**beginning of** <br>**period**<br>| **Net** <br>**investment** <br>**income** <br>**(loss)**<br>| **Net** <br>**realized** <br>**and** <br>**unrealized** <br>**gain (loss)**<br>| **Total from** <br>**investment** <br>**operations**<br>| **Distributions** <br>**from net** <br>**investment** <br>**income**<br>| **Distributions** <br>**from net** <br>**realized** <br>**gains**<br>| **Total** <br>**distributions to** <br>**shareholders**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | $23.87<br>| 0.31<br>| 5.25<br>| 5.56<br>| &nbsp;&nbsp; (0.56) <br>| &nbsp;&nbsp; (4.53) <br>| &nbsp;&nbsp; (5.09) <br>|
| Year Ended 12/31/2024 | $25.55<br>| 0.02<br>| &nbsp;&nbsp; (1.12) <br>| &nbsp;&nbsp; (1.10) <br>| &nbsp;&nbsp; (0.58) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.58) <br>|
| Year Ended 12/31/2023 | $20.61<br>| 0.06<br>| 5.04<br>| 5.10<br>| &nbsp;&nbsp; (0.16) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.16) <br>|
| Year Ended 12/31/2022 | $33.33<br>| 0.06 <br><sup>(e)</sup><br>| &nbsp;&nbsp; (12.78) <br>| &nbsp;&nbsp; (12.72) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2021 | $27.49<br>| &nbsp;&nbsp; (0.14) <br>| 6.04<br>| 5.90<br>| &nbsp;&nbsp; (0.06) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.06) <br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | $24.06<br>| 0.40<br>| 5.29<br>| 5.69<br>| &nbsp;&nbsp; (0.63) <br>| &nbsp;&nbsp; (4.53) <br>| &nbsp;&nbsp; (5.16) <br>|
| Year Ended 12/31/2024 | $25.76<br>| 0.08<br>| &nbsp;&nbsp; (1.14) <br>| &nbsp;&nbsp; (1.06) <br>| &nbsp;&nbsp; (0.64) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.64) <br>|
| Year Ended 12/31/2023 | $20.77<br>| 0.11<br>| 5.10<br>| 5.21<br>| &nbsp;&nbsp; (0.22) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.22) <br>|
| Year Ended 12/31/2022 | $33.51<br>| 0.11 <br><sup>(e)</sup><br>| &nbsp;&nbsp; (12.85) <br>| &nbsp;&nbsp; (12.74) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; —<br>|
| Year Ended 12/31/2021 | $27.64<br>| &nbsp;&nbsp; (0.06) <br>| 6.06<br>| 6.00<br>| &nbsp;&nbsp; (0.13) <br>| &nbsp;&nbsp; —<br>| &nbsp;&nbsp; (0.13) <br>|

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | |
|:---|:---|
| **Notes to Financial Highlights**  | **Notes to Financial Highlights**  |
| (a) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund's reported expense ratios. |
| (b) | Total net expenses include the impact of certain fee waivers/expense reimbursements made by the Investment Manager and certain of its affiliates, if applicable.  |
| (c) | Ratios include line of credit interest expense which is less than 0.01%.  |
| (d) | The benefits derived from expense reductions had an impact of less than 0.01%. |
| (e) | Net investment income per share includes special dividends. The effect of these dividends amounted to $0.01 per share. |
| (f) | Ratios include Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations. If these had been excluded, expenses would have been higher by 0.01%.  |

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Financial Highlights (continued)

Columbia Acorn European Fund<sup>SM</sup>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**asset** <br>**value,** <br>**end of** <br>**period**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Total** <br>**return**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net investment** <br>**income (loss)** <br>**ratio to** <br>**average** <br>**net assets**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Portfolio** <br>**turnover**<br>| &nbsp;&nbsp;&nbsp;&nbsp; **Net** <br>**assets,** <br>**end of** <br>**period** <br>**(000's)**<br>|
| **Class A** | **Class A** | **Class A** | **Class A** | **Class A** | **Class A** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $24.34<br>| &nbsp;&nbsp;&nbsp;&nbsp; 23.85%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.82% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.34% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.15%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 82%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $23745<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $23.87<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4.39%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.97% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.45% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.08%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 47%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $23057<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.55<br>| &nbsp;&nbsp;&nbsp;&nbsp; 24.76%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.92% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.45% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.24%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 23%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $30487<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $20.61<br>| &nbsp;&nbsp;&nbsp;&nbsp; (38.16%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.80% <br><sup>(c),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.45% <br><sup>(c),(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.25%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 31%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $28892<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.33<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.47%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.63% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.44% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.45%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $66374<br>|
| **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** | **Institutional Class** |
| Year Ended 12/31/2025 | &nbsp;&nbsp;&nbsp;&nbsp; $24.59<br>| &nbsp;&nbsp;&nbsp;&nbsp; 24.20%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.57% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.10% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 1.46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 82%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $12928<br>|
| Year Ended 12/31/2024 | &nbsp;&nbsp;&nbsp;&nbsp; $24.06<br>| &nbsp;&nbsp;&nbsp;&nbsp; (4.18%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.72% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.20% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.32%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 47%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $18053<br>|
| Year Ended 12/31/2023 | &nbsp;&nbsp;&nbsp;&nbsp; $25.76<br>| &nbsp;&nbsp;&nbsp;&nbsp; 25.09%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.67% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.20% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.47%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 23%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $23802<br>|
| Year Ended 12/31/2022 | &nbsp;&nbsp;&nbsp;&nbsp; $20.77<br>| &nbsp;&nbsp;&nbsp;&nbsp; (38.02%) <br>&nbsp;&nbsp;&nbsp;&nbsp; 1.54% <br><sup>(c),(f)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.20% <br><sup>(c),(d),(f)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; 0.46%<br>| &nbsp;&nbsp;&nbsp;&nbsp; 31%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $38307<br>|
| Year Ended 12/31/2021 | &nbsp;&nbsp;&nbsp;&nbsp; $33.51<br>| &nbsp;&nbsp;&nbsp;&nbsp; 21.76%<br>&nbsp;&nbsp;&nbsp;&nbsp; 1.38% <br><sup>(c)</sup><br>&nbsp;&nbsp;&nbsp;&nbsp; 1.19% <br><sup>(c),(d)</sup><br>| &nbsp;&nbsp;&nbsp;&nbsp; (0.21%) <br>| &nbsp;&nbsp;&nbsp;&nbsp; 21%<br>| &nbsp;&nbsp;&nbsp;&nbsp; $111462<br>|

---

The accompanying Notes to Financial Statements are an integral part of this statement.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements

December 31, 2025

Note 1. Organization

Columbia Acorn<sup>®</sup> Fund, Columbia Acorn International<sup>®</sup>, Columbia Acorn International Select<sup>SM</sup>, Columbia Thermostat Fund<sup>SM</sup> and Columbia Acorn European Fund<sup>SM</sup> (each a Fund and collectively, the Funds) are each a series of Columbia Acorn Trust (the Trust). The Trust is registered under the Investment Company Act of 1940, as amended (the 1940 Act), as an open-end management investment company organized as a Massachusetts business trust. Each Fund is a diversified fund.

Columbia Thermostat Fund<sup>SM</sup> is a "fund of funds", investing significantly in affiliated funds managed by Columbia Management Investment Advisers, LLC (the Investment Manager or Columbia Management), a wholly-owned subsidiary of Ameriprise Financial, Inc. (Ameriprise Financial), or its affiliates (Underlying Funds). Columbia Thermostat Fund<sup>SM</sup> is exposed to the same risks as the Underlying Funds in direct proportion to the allocation of its assets among the Underlying Funds. For information on the investment strategies, operations and risks of the Underlying Funds, please refer to the Fund's current prospectus as well as the prospectuses and shareholder reports of the Underlying Funds, which are available from the Securities and Exchange Commission website at www.sec.gov or on the Underlying Funds' website at columbiathreadneedleus.com/investor.

**Fund shares**

The Trust may issue an unlimited number of shares (without par value). The Funds currently offer the share classes listed in the Statement of Assets and Liabilities. Although all share classes generally have identical voting, dividend and liquidation rights, each share class votes separately when required by the Trust's organizational documents or by law. Each share class has its own expense and sales charge structure. Different share classes may have different minimum initial investment amounts and pay different net investment income distribution amounts to the extent the expenses of distributing such share classes vary. Distributions to shareholders in a liquidation event will be proportional to the net asset value of each share class.

As described in each Fund's prospectus, Class A and Class C shares are available to the general public for investment. Class C shares automatically convert to Class A shares of the same Fund after 8 years. Institutional Class, Institutional 2 Class, Institutional 3 Class and Class S shares are available for purchase through authorized investment professionals to omnibus retirement plans and to certain other investors as also described in each Fund's prospectus.

Note 2. Summary of significant accounting policies

**Basis of preparation** 

Each Fund is an investment company that applies the accounting and reporting guidance in the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946, *Financial Services - Investment Companies (ASC 946).* The financial statements are prepared in accordance with U.S. generally accepted accounting principles (GAAP), which requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates.

The following is a summary of significant accounting policies followed by the Funds in the preparation of their financial statements.

**Segment reporting**

The intent of FASB Accounting Standards Update 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures is to enable investors to better understand an entity's overall performance and to assess its potential future cash flows through improved segment disclosures. Prior to July 7, 2025, the chief operating decision maker (CODM) was Columbia Wanger Asset Management, LLC (CWAM), a wholly-owned subsidiary of Columbia Management. Effective July 7, 2025, Columbia Management is the CODM. The CODM, through its Investment Oversight Committee and Global Executive Group, is responsible for assessing performance and making decisions about resource allocation. The CODM has determined that the Funds have a single operating segment because the CODM monitors the operating results of the Funds

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

as a whole and the Funds' long-term strategic asset allocation is pre-determined in accordance with the terms of each Fund's prospectus, based on a defined investment strategy which is executed by the Funds' portfolio managers as a team. The financial information provided to and reviewed by the CODM is consistent with that presented within the Funds' financial statements.

**Security valuation**

Equity securities listed on an exchange are valued at the closing price or last trade price on their primary exchange at the close of business of the New York Stock Exchange. Securities with a closing price not readily available or not listed on any exchange are valued at the mean between the closing bid and ask prices. Listed preferred stocks convertible into common stocks are valued using an evaluated price from a pricing service.

Foreign equity securities are valued based on the closing price or last trade price on their primary exchange at the close of business of the New York Stock Exchange. If any foreign equity security closing prices are not readily available, the securities are valued at the mean of the latest quoted bid and ask prices on such exchanges or markets. Foreign currency exchange rates are determined at the scheduled closing time of the New York Stock Exchange. Many securities markets and exchanges outside the U.S. close prior to the close of the New York Stock Exchange; therefore, the closing prices for securities in such markets or on such exchanges may not fully reflect events that occur after such close but before the close of the New York Stock Exchange. In those situations, foreign securities will be fair valued pursuant to a policy approved by the Board of Trustees. Under the policy, the Fund may utilize a third-party pricing service to determine these fair values. The third-party pricing service takes into account multiple factors, including relevant general and sector indices, currency fluctuations, depositary receipts, and futures, as applicable, to determine a good faith estimate that reasonably reflects the current market conditions as of the close of the New York Stock Exchange. The fair value of a security is likely to be different from the quoted or published price, if available.

Investments in open-end investment companies (other than exchange-traded funds (ETFs)), are valued at the latest net asset value reported by those companies as of the valuation time.

Investments for which market quotations are not readily available, or that have quotations which management believes are not reflective of market value or reliable, are valued at fair value as determined in good faith under procedures approved by the Board of Trustees. If a security or class of securities (such as foreign securities) is valued at fair value, such value is likely to be different from the quoted or published price for the security, if available.

The determination of fair value often requires significant judgment. To determine fair value, management may use assumptions including but not limited to future cash flows and estimated risk premiums. Multiple inputs from various sources may be used to determine fair value.

GAAP requires disclosure regarding the inputs and valuation techniques used to measure fair value and any changes in valuation inputs or techniques. In addition, investments shall be disclosed by major category. This information is disclosed following the Funds' Portfolio of Investments.

**Foreign currency transactions and translations** 

The values of all assets and liabilities denominated in foreign currencies are generally translated into U.S. dollars at exchange rates determined at the close of regular trading on the New York Stock Exchange. Net realized and unrealized gains (losses) on foreign currency transactions and translations include gains (losses) arising from the fluctuation in exchange rates between trade and settlement dates on securities transactions, gains (losses) arising from the disposition of foreign currency and currency gains (losses) between the accrual and payment dates on dividends, interest income and foreign withholding taxes.

For financial statement purposes, the Funds do not distinguish that portion of gains (losses) on investments which is due to changes in foreign exchange rates from that which is due to changes in market prices of the investments. Such fluctuations are included with the net realized and unrealized gains (losses) on investments in the Statement of Operations.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

**Security transactions**

Security transactions are accounted for on the trade date. Cost is determined and gains (losses) are based upon the specific identification method for both financial statement and federal income tax purposes.

**Income recognition**

Corporate actions and dividend income are generally recorded net of any non-reclaimable tax withholdings, on the ex-dividend date or upon receipt of an ex-dividend notification in the case of certain foreign securities.

The Funds may receive distributions from holdings in equity securities, business development companies (BDCs), exchange-traded funds (ETFs), limited partnerships (LPs), other regulated investment companies (RICs), and real estate investment trusts (REITs), which report information as to the tax character of their distributions annually. These distributions are allocated to dividend income, capital gain and return of capital based on actual information reported. Return of capital is recorded as a reduction of the cost basis of securities held. If the Fund no longer owns the applicable securities, return of capital is recorded as a realized gain. With respect to REITs, to the extent actual information has not yet been reported, estimates for return of capital are made by Columbia Management Investment Advisers, LLC (the Investment Manager), a wholly-owned subsidiary of Ameriprise Financial, Inc. (Ameriprise Financial). The Investment Manager's estimates are subsequently adjusted when the actual character of the distributions is disclosed by the REITs, which could result in a proportionate change in return of capital to shareholders.

Awards from class action litigation are recorded as a reduction of cost basis if the Fund still owns the applicable securities on the payment date. If the Fund no longer owns the applicable securities on the payment date, the proceeds are recorded as realized gains.

Income and capital gain distributions from the Underlying Funds, if any, are recorded on the ex-dividend date.

**Securities lending**

Effective November 30, 2025, the security lending program was terminated and any outstanding loans were recalled on or before the effective date. Each Fund, prior to November 30, 2025, except Columbia Thermostat Fund<sup>SM</sup>, had the ability to lend securities up to one-third of the value of its total assets to certain approved brokers, dealers, banks and or other institutional borrowers of securities that the Funds' securities lending agent had determined were credit worthy under guidelines established by the Board of Trustees, to earn additional income. The Funds retained the benefits of owning the securities, including the economic equivalent of dividends or interest generated by the security. The Funds also received a fee for the loan. The Funds had the ability to recall the loans at any time and could do so in order to vote proxies or to sell the loaned securities. Each loan was collateralized by cash that exceeded the value of the securities on loan. The market value of the loaned securities was determined daily at the close of business of a Fund and any additional required collateral was delivered to the Fund on the next business day. The Funds elected to invest the cash collateral in the Dreyfus Government Cash Management Fund, a third-party institutional government money market fund in accordance with investment guidelines contained in the securities lending agreement and approved by the Board of Trustees. The income earned from the securities lending program was paid to each Fund, net of any fees remitted to Goldman Sachs Agency Lending, the Funds' lending agent, and net of any borrower rebates. The Investment Manager did not retain any fees earned by the lending program. The net securities lending income earned for the year ended December 31, 2025 by each Fund is included in the Statement of Operations.

**Expenses**

General expenses of the Trust are allocated to the Funds and other funds of the Trust based upon relative net assets or other expense allocation methodologies determined by the nature of the expense. Expenses directly attributable to a Fund are charged to that Fund. Expenses directly attributable to a specific class of shares are charged to that share class.

**Determination of class net asset value** 

All income, expenses (other than class-specific expenses which are charged directly to that share class, as shown in the Statement of Operations) and realized and unrealized gains (losses) are allocated to each class of a Fund on a daily basis, based on the relative net assets of each class, for purposes of determining the net asset value of each class.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

**Federal income tax status**

For federal income tax purposes, each Fund is treated as a separate entity. The Funds intend to qualify each year as separate regulated investment companies under Subchapter M of the Internal Revenue Code, as amended, and will distribute substantially all of their investment company taxable income and net capital gain, if any, for their tax year, and as such will not be subject to federal income taxes. In addition, the Funds intend to distribute in each calendar year substantially all of their ordinary income, capital gain net income and certain other amounts, if any, such that the Funds should not be subject to federal excise tax. Therefore, no federal income or excise tax provisions are recorded.

Columbia Acorn International Select<sup>SM</sup> paid withholding and/or capital gain taxes on its investments in foreign jurisdictions during the period ended December 31, 2025. The Fund may also have received reclaims or refunds on taxes paid. Cash paid (received) on withholding and capital gain taxes, net of reclaims/refunds received, totaled $(3,371,128).

Taxes paid (net of reclaims/refunds received) with respect to the following jurisdictions represented 5% or more of that total:

---

| | |
|:---|:---|
| **Country** | **Income taxes paid (net of reclaims/refunds received) ($)** |
| India | 262094 |
| France | (3896571)<br>|
| Other | 263349 |
| Total income taxes paid (net of reclaims/refunds received) | (3371128)<br>|

---

**Foreign taxes**

The Funds may be subject to foreign taxes on income, gains on investments or currency repatriation, a portion of which may be recoverable. The Funds will accrue such taxes and recoveries, as applicable, based upon its current interpretation of tax rules and regulations that exist in the markets in which it invests.

Realized gains in certain countries may be subject to foreign taxes at the Fund level, based on statutory rates. Each Fund accrues for such foreign taxes on realized and unrealized gains at the appropriate rate for each jurisdiction, as applicable. The amount, if any, is disclosed as a liability in the Statement of Assets and Liabilities.

The Funds may file withholding tax reclaims in certain European Union countries to recover a portion of foreign taxes previously withheld on dividends earned, which may be reclaimable based upon certain provisions in the Treaty on the Functioning of the European Union (EU) and subsequent rulings by the European Court of Justice. A Fund may record a reclaim receivable when the amount is known, a Fund has received notice of a pending refund, and there are no significant uncertainties on collectability. Income received from EU reclaims is included in the Statement of Operations.

Columbia Acorn International<sup>®</sup> and Columbia Acorn International Select<sup>SM</sup> are seeking a closing agreement with the Internal Revenue Service to address any prior years' U.S. income tax liabilities attributable to Fund shareholders resulting from the recovery of European Union tax reclaims. The closing agreement will result in the Funds paying a portion of those taxes refunded to the IRS, on behalf of their shareholders, representing the estimated tax savings generated from foreign tax credits claimed by Fund shareholders on their tax returns in the prior years. The Funds have accrued a liability for the estimated IRS Closing Agreement costs, which is disclosed on the Statement of Assets and Liabilities. The actual amount may differ from the estimate due to additional reclaims received or interest due and that difference may be material.

**Distributions to shareholders**

Distributions from net investment income, if any, are declared and paid semi-annually. Net realized capital gains, if any, are distributed at least annually. Income distributions and capital gain distributions are determined in accordance with federal income tax regulations, which may differ from GAAP.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

**Guarantees and indemnifications** 

Under the Trust's organizational documents and, in some cases, by contract, its officers and trustees are indemnified against certain liabilities arising out of the performance of their duties to the Trust or its funds. In addition, certain of the Funds' contracts with their service providers contain general indemnification clauses. The Funds' maximum exposure under these arrangements is unknown since the amount of any future claims that may be made against the Funds cannot be determined, and the Funds have no historical basis for predicting the likelihood of any such claims.

Note 3. Fees and other transactions with affiliates

**Management services fees**

Prior to July 7, 2025, CWAM was the Investment Manager and furnished investment supervision to the Funds and was responsible for the overall management of the Funds' business affairs.

Prior to April 1, 2025, CWAM furnished investment advisory services to the Funds under an investment advisory agreement (the Advisory Agreement) and provided administrative services to the Funds under a separate administrative services agreement (the Administration Agreement). Effective April 1, 2025, the Funds entered into a new management services agreement (the Management Agreement) that combined the management services fee that was previously paid under the Advisory Agreement with the administrative services fee that was previously paid under the Administration Agreement. On June 26, 2025, the Funds' Board of Trustees approved a Novation of Management Agreement pursuant to which all rights, duties and obligations under the Funds' then-current Management Agreement with CWAM transferred to its parent company Columbia Management on July 7, 2025. Prior to July, 7, 2025, Columbia Management was the sub-administrator of the Funds and the investment adviser of each of the other Columbia funds except for each series of Columbia Funds Variable Series Trust (formerly Wanger Advisors Trust). The services provided to, and management fees paid by, the Funds did not change as a result of this transfer and the current portfolio managers of the Funds continued to manage the Funds after the transition.

For the period from January 1, 2025 through February 28, 2025, CWAM received an advisory fee based on each Fund's daily net assets that declined as each Fund's net assets increased at the following annual rates:

---

| | | | |
|:---|:---|:---|:---|
|  | **High (%)** | **Low (%)** | &nbsp;&nbsp;&nbsp; **Annualized** <br>**effective advisory** <br>**fee rate (%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.74 | &nbsp;&nbsp;&nbsp;&nbsp;0.63 | &nbsp;&nbsp;&nbsp;&nbsp;0.69 |
| Columbia Acorn International<sup>®</sup> | 1.10 | &nbsp;&nbsp;&nbsp;&nbsp;0.72 | &nbsp;&nbsp;&nbsp;&nbsp;0.86 |
| Columbia Acorn International Select<sup>SM</sup> | 0.89 | &nbsp;&nbsp;&nbsp;&nbsp;0.85 | &nbsp;&nbsp;&nbsp;&nbsp;0.89 |
| Columbia Thermostat Fund<sup>SM</sup> | 0.10 | &nbsp;&nbsp;&nbsp;&nbsp;0.10 | &nbsp;&nbsp;&nbsp;&nbsp;0.10 |
| Columbia Acorn European Fund<sup>SM</sup> | 1.19 | &nbsp;&nbsp;&nbsp;&nbsp;0.74 | &nbsp;&nbsp;&nbsp;&nbsp;1.19 |

---

Effective March 1, 2025, the Board of Trustees approved a reduction in the advisory fee rates payable to CWAM by the Funds, as noted below. For the period March 1, 2025 through March 31, 2025 CWAM received an advisory fee based on each Fund's daily net assets that declined as each Fund's net assets increased at the following annual rates:

---

| | | | |
|:---|:---|:---|:---|
|  | **High (%)** | **Low (%)** | &nbsp;&nbsp;&nbsp; **Annualized** <br>**effective advisory** <br>**fee rate (%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.74 | &nbsp;&nbsp;&nbsp;&nbsp;0.61 | &nbsp;&nbsp;&nbsp;&nbsp;0.67 |
| Columbia Acorn International<sup>®</sup> | 0.87 | &nbsp;&nbsp;&nbsp;&nbsp;0.70 | &nbsp;&nbsp;&nbsp;&nbsp;0.81 |
| Columbia Acorn International Select<sup>SM</sup> | 0.82 | &nbsp;&nbsp;&nbsp;&nbsp;0.63 | &nbsp;&nbsp;&nbsp;&nbsp;0.82 |
| Columbia Thermostat Fund<sup>SM</sup> | 0.10 | &nbsp;&nbsp;&nbsp;&nbsp;0.10 | &nbsp;&nbsp;&nbsp;&nbsp;0.10 |
| Columbia Acorn European Fund<sup>SM</sup> | 0.92 | &nbsp;&nbsp;&nbsp;&nbsp;0.74 | &nbsp;&nbsp;&nbsp;&nbsp;0.92 |

---

Advisory fees paid by the Funds for the period January 1, 2025 through March 31, 2025 are included in Management services fees on the Statement of Operations.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

For the period April 1, 2025 through December 31, 2025, the Investment Manager (CWAM prior to July 7, 2025 and Columbia Management beginning July 7, 2025) received a management services fee based on each Fund's daily net assets that declined as each Fund's net assets increased at the following annual rates:

---

| | | | |
|:---|:---|:---|:---|
|  | **High (%)** | **Low (%)** | &nbsp;&nbsp;&nbsp; **Annualized Effective** <br>**management services** <br>**fee rate (%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.790 | &nbsp;&nbsp;&nbsp;&nbsp;0.625 | &nbsp;&nbsp;&nbsp;&nbsp;0.722 |
| Columbia Acorn International<sup>®</sup> | 0.920 | &nbsp;&nbsp;&nbsp;&nbsp;0.715 | &nbsp;&nbsp;&nbsp;&nbsp;0.865 |
| Columbia Acorn International Select<sup>SM</sup> | 0.870 | &nbsp;&nbsp;&nbsp;&nbsp;0.645 | &nbsp;&nbsp;&nbsp;&nbsp;0.870 |
| Columbia Thermostat Fund<sup>SM</sup> | 0.100 | &nbsp;&nbsp;&nbsp;&nbsp;0.100 | &nbsp;&nbsp;&nbsp;&nbsp;0.100 |
| Columbia Acorn European Fund<sup>SM</sup> | 0.970 | &nbsp;&nbsp;&nbsp;&nbsp;0.755 | &nbsp;&nbsp;&nbsp;&nbsp;0.970 |

---

For the period January 1, 2025 through December 31, 2025, the effective blended advisory fee (for the period January 1, 2025 through March 31, 2025) and management services fee (for the period April 1, 2025 through December 31, 2025), as a percentage of each Fund's average daily net assets, were as follows:

---

| | |
|:---|:---|
|  | **Effective** <br>**blended** <br>**fee rate (%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.712 |
| Columbia Acorn International<sup>®</sup> | 0.859 |
| Columbia Acorn International Select<sup>SM</sup> | 0.869 |
| Columbia Thermostat Fund<sup>SM</sup> | 0.100 |
| Columbia Acorn European Fund<sup>SM</sup> | 1.00 |

---

**Participating Affiliates** 

The Investment Manager and its investment advisory affiliates (Participating Affiliates), may coordinate in providing services to their clients. These Participating Affiliates, like the Investment Manager, are direct or indirect subsidiaries of Ameriprise Financial and are registered with the appropriate respective regulators and, where required, the Securities and Exchange Commission and the Commodity Futures Trading Commission in the United States. The Investment Manager engages employees of Participating Affiliates to provide portfolio management services to the Funds. These employees provide services to the Investment Manager pursuant to personnel-sharing agreements or other inter-company arrangements and the Funds pay no additional fees and expenses as a result of any such arrangements.

Specifically, pursuant to such arrangements, employees of Participating Affiliates serve as "associated persons" of the Investment Manager and, in this capacity, serve as Fund portfolio managers and provide portfolio management services to the Funds on behalf of the Investment Manager subject to the oversight and supervision of the Investment Manager and the Funds' Chief Compliance Officer, consistent with the investment objectives, policies and limitations set forth in each Fund's prospectus and SAI, and the Investment Manager's and the Funds' compliance policies and procedures.

**Administration fees**

Prior to April 1, 2025, CWAM received an administration fee from the Funds at the following annual rates:

---

| | |
|:---|:---|
| **Columbia Acorn Trust** | **Columbia Acorn Trust** |
| **Aggregate average daily** <br>**net assets of the trust**<br>| **Annual** <br>**fee rate**<br>|
| Up to $8 billion | 0.050% |
| $8 billion to $16 billion | 0.040% |
| $16 billion to $35 billion | 0.030% |
| $35 billion to $45 billion | 0.025% |
| $45 billion and over | 0.015% |

---

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

For the period January 1, 2025 through March 31, 2025, the annualized effective administration fee rate was 0.050% of each Fund's average daily net assets, with the exception of Columbia Thermostat Fund<sup>SM</sup>. Columbia Thermostat Fund<sup>SM</sup> contractually waived administration fees for the period March 1, 2025 through March 31, 2025. For the period January 1, 2025 through March 31, 2025, the annualized effective administration fee rate, including the impact of administration fee waivers, for Columbia Thermostat Fund<sup>SM</sup> was 0.030% of the Fund's average daily net assets.

**Compensation of Board members** 

Members of the Board of Trustees who are not officers or employees of the Investment Manager or Ameriprise Financial are compensated for their services to the Funds as disclosed in the Statement of Operations. Under a Deferred Compensation Plan (the Deferred Plan), these members of the Board of Trustees may elect to defer payment of up to 100% of their compensation. Deferred amounts are treated as though equivalent dollar amounts had been invested in shares of certain funds managed by the Investment Manager. Each Fund's liability for these amounts is adjusted for market value changes and remains in the Funds until distributed in accordance with the Deferred Plan. All amounts payable under the Deferred Plan constitute a general unsecured obligation of the Funds. The expense for the Deferred Plan, which includes Trustees' fees deferred during the current period as well as any gains or losses on the Trustees' deferred compensation balances as a result of market fluctuations, is included in "Deferred compensation of board members" in the Statement of Operations.

**Compensation of Chief Compliance Officer**

The Board of Trustees has appointed a Chief Compliance Officer for the Funds in accordance with federal securities regulations. As disclosed in the Statement of Operations, a portion of the Chief Compliance Officer's total compensation is allocated to the Funds, along with other allocations to affiliated registered investment companies managed by the Investment Manager and its affiliates, based on relative net assets.

**Transfer agency fees**

Under a Transfer and Dividend Disbursing Agent Agreement, Columbia Management Investment Services Corp. (the Transfer Agent), an affiliate of the Investment Manager and a wholly-owned subsidiary of Ameriprise Financial, is responsible for providing transfer agency services to the Funds. The Transfer Agent has contracted with SS&C GIDS, Inc. (SS&C GIDS) to serve as sub-transfer agent. The Transfer Agent pays the fees of SS&C GIDS for services as sub-transfer agent and SS&C GIDS is not entitled to reimbursement for such fees from the Funds (with the exception of out-of-pocket fees).

The Funds pay the Transfer Agent a monthly transfer agency fee based on the number or the average value of accounts, depending on the type of account. In addition, the Funds pay the Transfer Agent a fee for shareholder services based on the number of accounts or on a percentage of the average aggregate value of a Fund's shares maintained in omnibus accounts up to the lesser of the amount charged by the financial intermediary or a cap established by the Board of Trustees from time to time.

The Transfer Agent also receives compensation from the Funds for various shareholder services and reimbursements for certain out-of-pocket fees. Total transfer agency fees for Institutional 2 Class and Institutional 3 Class shares are subject to an annual limitation of not more than 0.07% and 0.02%, respectively, of the average daily net assets attributable to each share class. Prior to May 1, 2025, Institutional 2 Class shares were subject to a contractual transfer agency fee annual limitation of not more than 0.05% and Institutional 3 Class shares were subject to a contractual transfer agency fee annual limitation of not more than 0.00% of the average daily net assets attributable to each share class for Columbia Acorn International Select<sup>SM</sup>. In addition, prior to May 1, 2025, Institutional 2 Class shares were subject to a contractual transfer agency fee annual limitation of not more than 0.04% and Institutional 3 Class shares were subject to a contractual transfer agency fee annual limitation of not more than 0.00% of the average daily net assets attributable to each share class for Columbia Thermostat Fund<sup>SM</sup>.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

For the year ended December 31, 2025, each Fund's effective transfer agency fee rate as a percentage of average daily net assets was as follows:

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
| **Fund**  | **Class A** <br>**(%)**<br>| **Class C** <br>**(%)**<br>| **Institutional** <br>**Class (%)**<br>| **Institutional 2** <br>**Class (%)**<br>| **Institutional 3** <br>**Class (%)**<br>| **Class S** <br>**(%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.09 | 0.09 | 0.09 | 0.05 | 0.01 | 0.09 |
| Columbia Acorn International<sup>®</sup> | 0.11 | &nbsp;&nbsp; — | 0.11 | 0.05 | 0.00 | 0.11 |
| Columbia Acorn International Select<sup>SM</sup> | 0.19 | &nbsp;&nbsp; — | 0.19 | 0.05 | 0.00 | 0.19 |
| Columbia Thermostat Fund<sup>SM</sup> | 0.09 | 0.09 | 0.09 | 0.05 | 0.01 | 0.09 |
| Columbia Acorn European Fund<sup>SM</sup> | 0.12 | &nbsp;&nbsp; — | 0.12 | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — |

---

An annual minimum account balance fee of $20 may apply to certain accounts with a value below the applicable share class's initial minimum investment requirements to reduce the impact of small accounts on transfer agency fees. These minimum account balance fees are remitted to the Funds and recorded as part of expense reductions in the Statement of Operations.

For the year ended December 31, 2025, these minimum account balance fees reduced total expenses as follows:

---

| | |
|:---|:---|
| **Fund**  | **Amount ($)**  |
| Columbia Acorn<sup>®</sup> Fund | 4994 |
| Columbia Acorn International<sup>®</sup> | 3851 |
| Columbia Acorn International Select<sup>SM</sup> | 5620 |
| Columbia Thermostat Fund<sup>SM</sup> | 80 |
| Columbia Acorn European Fund<sup>SM</sup> | 40 |

---

**Distribution and service fees**

The Funds have entered into an agreement with Columbia Management Investment Distributors, Inc. (the Distributor), an affiliate of the Investment Manager and a wholly-owned subsidiary of Ameriprise Financial, for distribution and shareholder services. The Board of Trustees has approved, and the Funds have adopted, distribution and shareholder service plans (the Plans) applicable to certain share classes, which set the distribution and service fees for the Funds. These fees are calculated daily and are intended to compensate the Distributor and/or eligible selling and/or servicing agents for selling shares of the Funds and providing services to investors.

Under the Plans, the Funds pay a monthly service fee to the Distributor at the maximum annual rate of 0.25% of the average daily net assets attributable to Class A and Class C shares of the Funds. Also under the Plans, the Funds pay a monthly distribution fee to the Distributor at the maximum annual rate of 0.75% of the average daily net assets attributable to Class C shares of the Funds.

**Sales charges (unaudited)**

Sales charges, including front-end charges and contingent deferred sales charges (CDSCs), received by the Distributor for distributing Fund shares for the year ended December 31, 2025, if any, are listed below:

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | **Front End (%)** | **Front End (%)** | **CDSC (%)** | **Amount ($)** | **Amount ($)** |
| **Fund**  | **Class A**  | **Class C**  | **Class C**  | **Class A**  | **Class C**  |
| Columbia Acorn<sup>®</sup> Fund | 5.75 | &nbsp;&nbsp; —<br> 0.50 - 1.00 <br><sup>(a)</sup><br>| 1.00 <br><sup>(b)</sup><br>| &nbsp;&nbsp; 37942 | &nbsp;&nbsp; 789 |
| Columbia Acorn International<sup>®</sup> | 5.75 | &nbsp;&nbsp; —<br> 0.50 - 1.00 <br><sup>(a)</sup><br>| 1.00 <br><sup>(b)</sup><br>| &nbsp;&nbsp; 19549 | &nbsp;&nbsp; — |
| Columbia Acorn International Select<sup>SM</sup> | 5.75 | &nbsp;&nbsp; —<br> 0.50 - 1.00 <br><sup>(a)</sup><br>| &nbsp;&nbsp; — | &nbsp;&nbsp; 13667 | &nbsp;&nbsp; — |
| Columbia Thermostat Fund<sup>SM</sup> | 5.75 | &nbsp;&nbsp; —<br> 0.50 - 1.00 <br><sup>(a)</sup><br>| 1.00 <br><sup>(b)</sup><br>| &nbsp;&nbsp; 165556 | &nbsp;&nbsp; 3519 |
| Columbia Acorn European Fund<sup>SM</sup> | 5.75 | &nbsp;&nbsp; —<br> 0.50 - 1.00 <br><sup>(a)</sup><br>| &nbsp;&nbsp; — | &nbsp;&nbsp; 10558 | &nbsp;&nbsp; — |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;(a) This charge is imposed on certain investments of between $1 million and $50 million redeemed within 18 months after purchase, as follows: 1.00% if redeemed within 12 months after purchase, and 0.50% if redeemed more than 12, but less than 18, months after purchase, with certain limited exceptions.

&nbsp;&nbsp;&nbsp;&nbsp;(b) This charge applies to redemptions within 12 months after purchase, with certain limited exceptions.

The Funds' other share classes are not subject to sales charges.

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

**Expenses waived/reimbursed by the Investment Manager and its affiliates**

The Investment Manager and certain of its affiliates have contractually agreed to waive fees and/or reimburse expenses (excluding certain fees and expenses described below) for the period(s) disclosed below, unless sooner terminated at the sole discretion of the Board of Trustees, so that each Fund's net operating expenses, after giving effect to fees waived/expenses reimbursed and any balance credits and/or overdraft charges from the Funds' custodian, do not exceed the following annual rate(s) as a percentage of the classes' average daily net assets:

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **March 1, 2025 through April 30, 2027** | **March 1, 2025 through April 30, 2027** | **March 1, 2025 through April 30, 2027** | **March 1, 2025 through April 30, 2027** | **March 1, 2025 through April 30, 2027** | **March 1, 2025 through April 30, 2027** |
| **Fund** | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class A** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class C** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 2** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 3** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class S** <br>**(%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.07 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.82 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.82 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.78 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.74 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.82 |
| Columbia Acorn International<sup>®</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.22 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.97 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.89 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.84 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.97 |
| Columbia Thermostat Fund<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.50 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.25 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.25 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.20 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.16 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.25 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** |
| **Fund** | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class A** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class C** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 2** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 3** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class S** <br>**(%)**<br>|
| Columbia Acorn<sup>®</sup> Fund | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.08 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.83 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.83 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.80 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.75 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.83 |
| Columbia Acorn International<sup>®</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.23 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.98 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.92 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.88 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.98 |
| Columbia Thermostat Fund<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.50 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.25 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.25 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.20 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.16 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.25 |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | **May 1, 2025 through April 30, 2026** | **May 1, 2025 through April 30, 2026** | **May 1, 2025 through April 30, 2026** | **May 1, 2025 through April 30, 2026** | **May 1, 2025 through April 30, 2026** |
| **Fund** | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class A** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 2** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 3** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class S** <br>**(%)**<br>|
| Columbia Acorn International Select<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.11 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.86 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.72 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.67 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.86 |
| Columbia Acorn European Fund<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.31 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.06 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | **March 1, 2025 through April 30, 2025** | **March 1, 2025 through April 30, 2025** | **March 1, 2025 through April 30, 2025** | **March 1, 2025 through April 30, 2025** | **March 1, 2025 through April 30, 2025** |
| **Fund** | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class A** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 2** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 3** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class S** <br>**(%)**<br>|
| Columbia Acorn International Select<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.14 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.89 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.75 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.70 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.89 |
| Columbia Acorn European Fund<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.37 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.12 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
|  | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** | **Prior to March 1, 2025** |
| **Fund** | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class A** <br>**(%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 2** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Institutional 3** <br>**Class (%)**<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Class S** <br>**(%)**<br>|
| Columbia Acorn International Select<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.24 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.99 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.84 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.79 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0.99 |
| Columbia Acorn European Fund<sup>SM</sup> | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.45 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.20 | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N/A |

---

Under the agreement governing these fee waivers and/or expense reimbursement arrangements, the following fees and expenses are excluded from the waiver/reimbursement commitment, and therefore will be paid by each Fund, if applicable: taxes (including foreign transaction taxes), expenses associated with investments in affiliated and non-affiliated pooled investment vehicles (including mutual funds and exchange-traded funds), transaction costs and brokerage commissions, costs related to any securities lending program, dividend expenses associated with securities sold short, inverse floater program fees and expenses, transaction charges and interest on borrowed money, interest, costs associated with shareholder meetings, infrequent and/or unusual expenses and any other expenses the exclusion of which is specifically approved by the Board of Trustees. This agreement may be modified or amended only with approval from the Investment Manager, certain of its affiliates and the Fund. In addition to the contractual agreement, the Investment Manager and certain of its affiliates have voluntarily agreed to waive fees and/or reimburse Columbia Acorn International<sup>®</sup> expenses (excluding certain fees and expenses described above) so that Columbia Acorn International<sup>®</sup> level expenses (expenses directly attributable to Columbia Acorn International<sup>®</sup> and not to a specific share class) are waived proportionately across all share classes, but Columbia Acorn International<sup>®</sup> net operating expenses shall not exceed the contractual annual rates listed in the table above. This arrangement may be revised or discontinued at any time. Any fees waived and/or expenses

Columbia Acorn Trust \| 2025

------

Notes to Financial Statements (continued)

December 31, 2025

reimbursed under the expense reimbursement arrangements described above are not recoverable by the Investment Manager or its affiliates in future periods. Reflected in the contractual cap commitment, prior to May 1, 2025, is the Transfer Agent's contractual agreement to limit total transfer agency fees to an annual rate of not more than 0.05% for Institutional 2 Class and 0.00% for Institutional 3 of the average daily net assets attributable to each share class for Columbia Acorn International Select<sup>SM</sup>. In addition, reflected in the contractual cap commitment, prior to May 1, 2025, is the Transfer Agent's contractual agreement to limit total transfer agency fees to an annual rate of not more than 0.04% for Institutional 2 Class and 0.00% for Institutional 3 of the average daily net assets attributable to each share class for Columbia Thermostat Fund<sup>SM</sup>.

Note 4. Federal tax information

The timing and character of income and capital gain distributions are determined in accordance with income tax regulations, which may differ from GAAP because of temporary or permanent book to tax differences.

At December 31, 2025, these differences were primarily due to differing treatment for deferral/reversal of wash sale losses, passive foreign investment company (pfic) holdings, late-year ordinary losses, capital loss carryforwards, trustees' deferred compensation, net operating loss reclassification, foreign currency transactions, re-characterization of distributions for investments, excess distributions, distribution reclassifications, foreign capital gains tax and miscellaneous adjustments. To the extent these differences were permanent, reclassifications were made among the components of the Fund's net assets. Temporary differences do not require reclassifications.

The following reclassifications were made:

---

| | | | |
|:---|:---|:---|:---|
| **Fund**  | **Undistributed** <br>**(excess of distributions over)** <br>**net investment income ($)**<br>| &nbsp;&nbsp;&nbsp; **Accumulated** <br>**net realized** <br>**gain (loss) ($)**<br>| &nbsp;&nbsp;&nbsp; **Paid in capital** <br>**decrease ($)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 10205258 | &nbsp;&nbsp;&nbsp;&nbsp; (222877)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (9982381)<br>|
| Columbia Acorn International<sup>®</sup> | 4455532 | &nbsp;&nbsp;&nbsp;&nbsp; (4455532)<br>| &nbsp;&nbsp;&nbsp;&nbsp; — |
| Columbia Acorn International Select<sup>SM</sup> | 1496056 | &nbsp;&nbsp;&nbsp;&nbsp; (1331407)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (164649)<br>|
| Columbia Thermostat Fund<sup>SM</sup> | 3793644 | &nbsp;&nbsp;&nbsp;&nbsp; (3793644)<br>| &nbsp;&nbsp;&nbsp;&nbsp; — |
| Columbia Acorn European Fund<sup>SM</sup> | 701735 | &nbsp;&nbsp;&nbsp;&nbsp; (548697)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (153038)<br>|

---

Net investment income (loss) and net realized gains (losses), as disclosed in the Statement of Operations, and net assets were not affected by these reclassifications.

The tax character of distributions paid during the years indicated was as follows:

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **Year Ended December 31, 2025** | **Year Ended December 31, 2025** | **Year Ended December 31, 2025** | **Year Ended December 31, 2024** | **Year Ended December 31, 2024** | **Year Ended December 31, 2024** |
| **Fund**  | **Ordinary** <br>**income ($)**<br>| **Long-term** <br>**capital gains ($)**<br>| **Total ($)** | **Ordinary** <br>**income ($)**<br>| **Long-term** <br>**capital gains ($)**<br>| **Total ($)** |
| Columbia Acorn<sup>®</sup> Fund |  | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — | &nbsp;&nbsp; — |
| Columbia Acorn International<sup>®</sup> | 12424487 | &nbsp;&nbsp; 35707713 | &nbsp;&nbsp; 48132200 | &nbsp;&nbsp; 32706710 | &nbsp;&nbsp; 77255186 | &nbsp;&nbsp; 109961896 |
| Columbia Acorn International Select<sup>SM</sup> | 11938055 | &nbsp;&nbsp; 900259 | &nbsp;&nbsp; 12838314 | &nbsp;&nbsp; 2132987 | &nbsp;&nbsp; — | &nbsp;&nbsp; 2132987 |
| Columbia Thermostat Fund<sup>SM</sup> | 40846464 | &nbsp;&nbsp; — | &nbsp;&nbsp; 40846464 | &nbsp;&nbsp; 40091566 | &nbsp;&nbsp; — | &nbsp;&nbsp; 40091566 |
| Columbia Acorn European Fund<sup>SM</sup> | 742404 | &nbsp;&nbsp; 5760015 | &nbsp;&nbsp; 6502419 | &nbsp;&nbsp; 1101985 | &nbsp;&nbsp; — | &nbsp;&nbsp; 1101985 |

---

Short-term capital gain distributions, if any, are considered ordinary income distributions for tax purposes.

Columbia Acorn Trust \| 2025

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Notes to Financial Statements (continued)

December 31, 2025

At December 31, 2025, the components of distributable earnings on a tax basis were as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
| **Fund**  | **Undistributed** <br>**ordinary** <br>**income ($)**<br>| &nbsp;&nbsp;&nbsp; **Undistributed** <br>**long-term** <br>**capital gains ($)**<br>| &nbsp;&nbsp;&nbsp; **Capital loss** <br>**carryforwards ($)**<br>| &nbsp;&nbsp;&nbsp; **Net unrealized** <br>**appreciation ($)**<br>|
| Columbia Acorn<sup>®</sup> Fund |  | &nbsp;&nbsp;&nbsp;&nbsp; 25345146 | &nbsp;&nbsp;&nbsp;&nbsp; (3367063)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 408947180 |
| Columbia Acorn International<sup>®</sup> | 5442107 | &nbsp;&nbsp;&nbsp;&nbsp; 7617177 | &nbsp;&nbsp;&nbsp;&nbsp; (72593166)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 207859962 |
| Columbia Acorn International Select<sup>SM</sup> |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 35446126 |
| Columbia Thermostat Fund<sup>SM</sup> | 5249945 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; (55531268)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 81116696 |
| Columbia Acorn European Fund<sup>SM</sup> |  | &nbsp;&nbsp;&nbsp;&nbsp; 113801 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 4664777 |

---

At December 31, 2025, the cost of all investments for federal income tax purposes along with the aggregate gross unrealized appreciation and depreciation based on that cost was:

---

| | | | | |
|:---|:---|:---|:---|:---|
| **Fund**  | **Tax cost ($)** | &nbsp;&nbsp;&nbsp; **Gross** <br>**unrealized** <br>**appreciation ($)**<br>| &nbsp;&nbsp;&nbsp; **Gross** <br>**unrealized** <br>&nbsp;&nbsp;&nbsp;&nbsp;**(depreciation) ($)**<br>| &nbsp;&nbsp;&nbsp; **Net unrealized** <br>**appreciation ($)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 2025490440 | &nbsp;&nbsp;&nbsp;&nbsp; 566703336 | &nbsp;&nbsp;&nbsp;&nbsp; (157756156)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 408947180 |
| Columbia Acorn International<sup>®</sup> | 599864882 | &nbsp;&nbsp;&nbsp;&nbsp; 236083699 | &nbsp;&nbsp;&nbsp;&nbsp; (28223737)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 207859962 |
| Columbia Acorn International Select<sup>SM</sup> | 165121407 | &nbsp;&nbsp;&nbsp;&nbsp; 44999528 | &nbsp;&nbsp;&nbsp;&nbsp; (9553402)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 35446126 |
| Columbia Thermostat Fund<sup>SM</sup> | 1216068730 | &nbsp;&nbsp;&nbsp;&nbsp; 81116696 | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 81116696 |
| Columbia Acorn European Fund<sup>SM</sup> | 31486783 | &nbsp;&nbsp;&nbsp;&nbsp; 5736611 | &nbsp;&nbsp;&nbsp;&nbsp; (1071834)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 4664777 |

---

Tax cost of investments and unrealized appreciation/(depreciation) may also include timing differences that do not constitute adjustments to tax basis.

The following capital loss carryforwards, determined at December 31, 2025, may be available to reduce future net realized gains on investments, if any, to the extent permitted by the Internal Revenue Code. In addition, for the year ended December 31, 2025, capital loss carryforwards utilized, if any, were as follows:

---

| | | | | |
|:---|:---|:---|:---|:---|
| **Fund**  | **No expiration** <br>**short-term ($)**<br>| &nbsp;&nbsp;&nbsp; **No expiration** <br>**long-term ($)**<br>| **Total ($)** | **Utilized ($)** |
| Columbia Acorn<sup>®</sup> Fund | (2163220)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (1203843)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (3367063)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 178835157 |
| Columbia Acorn International<sup>®</sup> | (46324067)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (26269099)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (72593166)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 288119 |
| Columbia Acorn International Select<sup>SM</sup> |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 9143290 |
| Columbia Thermostat Fund<sup>SM</sup> |  | &nbsp;&nbsp;&nbsp;&nbsp; (55531268)<br>| &nbsp;&nbsp;&nbsp;&nbsp; (55531268)<br>| &nbsp;&nbsp;&nbsp;&nbsp; 61326898 |
| Columbia Acorn European Fund<sup>SM</sup> |  | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; — | &nbsp;&nbsp;&nbsp;&nbsp; 5586840 |

---

Under current tax rules, regulated investment companies can elect to treat certain late-year ordinary losses incurred and post-October capital losses (capital losses realized after October 31) as arising on the first day of the following taxable year. As of December 31, 2025, the Funds will elect to treat the following late-year ordinary losses and post-October capital losses as arising on January 1, 2026.

---

| | | |
|:---|:---|:---|
| **Fund**  | **Late year** <br>**ordinary losses ($)**<br>| &nbsp;&nbsp;&nbsp; **Post-October** <br>**capital losses ($)**<br>|
| Columbia Acorn International Select<sup>SM</sup> | 539229 | &nbsp;&nbsp;&nbsp;&nbsp; — |

---

Management of the Funds has concluded that there are no significant uncertain tax positions in the Funds that would require recognition in the financial statements. However, management's conclusion may be subject to review and adjustment at a later date based on factors including, but not limited to, new tax laws, regulations, and administrative interpretations (including relevant court decisions). Generally, the Funds' federal tax returns for the prior three fiscal years remain subject to examination by the Internal Revenue Service.

Columbia Acorn Trust \| 2025

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Notes to Financial Statements (continued)

December 31, 2025

Note 5. Portfolio information

For the year ended December 31, 2025, the cost of purchases and proceeds from sales of securities, excluding short-term investments and derivatives, if any, for each Fund aggregated to:

---

| | | |
|:---|:---|:---|
|  | **Purchases** <br>**($)**<br>| &nbsp;&nbsp;&nbsp; **Proceeds** <br>**from sales** <br>**($)**<br>|
| Columbia Acorn<sup>®</sup> Fund | 1931766411 | &nbsp;&nbsp;&nbsp;&nbsp; 2329201591 |
| Columbia Acorn International<sup>®</sup> | 219254031 | &nbsp;&nbsp;&nbsp;&nbsp; 390662853 |
| Columbia Acorn International Select<sup>SM</sup> | 41053121 | &nbsp;&nbsp;&nbsp;&nbsp; 60918010 |
| Columbia Thermostat Fund<sup>SM</sup> | 1038130863 | &nbsp;&nbsp;&nbsp;&nbsp; 1040089397 |
| Columbia Acorn European Fund<sup>SM</sup> | 32048216 | &nbsp;&nbsp;&nbsp;&nbsp; 44646281 |

---

The amount of purchase and sale activity impacts the portfolio turnover rate reported in the Financial Highlights.

Note 6. Affiliated money market fund

Each Fund may invest in Columbia Short-Term Cash Fund, an affiliated money market fund established for the exclusive use by each Fund and other affiliated funds (the Affiliated MMF). The income earned by the Funds from such investments is included as Dividends - affiliated issuers in the Statement of Operations. As an investing fund, each Fund indirectly bears its proportionate share of the expenses of the Affiliated MMF. The Affiliated MMF prices its shares with a floating net asset value. The Securities and Exchange Commission has adopted amendments to money market fund rules requiring institutional prime money market funds like the Affiliated MMF to be subject to a discretionary liquidity fee of up to 2% if the imposition of such a fee is determined to be in the best interest of the Affiliated MMF and to a mandatory liquidity fee if daily net redemptions exceed 5% of net assets.

Note 7. Line of credit

Each Fund has access to a revolving credit facility with a syndicate of banks led by JPMorgan Chase Bank, N.A., Citibank, N.A. and Wells Fargo Bank, N.A. whereby the Fund may borrow for the temporary funding of shareholder redemptions or for other temporary or emergency purposes. Pursuant to an October 23, 2025 amendment and restatement, the credit facility, which is an agreement between the Fund and certain other funds managed by the Investment Manager or an affiliated investment manager, severally and not jointly, permits aggregate borrowings up to $750 million. Interest is currently charged to each participating fund based on its borrowings at a rate equal to the higher of (i) the federal funds effective rate, (ii) the secured overnight financing rate plus 0.10% and (iii) the overnight bank funding rate, plus 1.00% in each case. Each borrowing under the credit facility matures no later than 60 days after the date of borrowing. The Fund also pays a commitment fee equal to its pro rata share of the unused amount of the credit facility at a rate of 0.15% per annum. The commitment fee is included in other expenses in the Statement of Operations. This agreement expires annually in October unless extended or renewed. Prior to the October 23, 2025 amendment and restatement, each Fund had access to a revolving credit facility with a syndicate of banks led by JPMorgan Chase Bank, N.A., Citibank, N.A. and Wells Fargo Bank, N.A. which permitted collective borrowings up to $900 million. Interest was charged to each participating fund based on its borrowings at a rate equal to the higher of (i) the federal funds effective rate, (ii) the secured overnight financing rate plus 0.10% and (iii) the overnight bank funding rate, plus 1.00% in each case.

During the year ended December 31, 2025, the following Funds had borrowings:

---

| | | | |
|:---|:---|:---|:---|
| **Fund** | **Average loan** <br>**balance ($)**<br>| &nbsp;&nbsp;&nbsp; **Weighted average** <br>**interest rate (%)**<br>| &nbsp;&nbsp;&nbsp; **Days** <br>**outstanding**<br>|
| Columbia Acorn International<sup>®</sup> | 2600000 | &nbsp;&nbsp;&nbsp;&nbsp;5.32 | &nbsp;&nbsp;&nbsp;&nbsp; 11 |
| Columbia Acorn International Select<sup>SM</sup> | 200000 | &nbsp;&nbsp;&nbsp;&nbsp;5.38 | &nbsp;&nbsp;&nbsp;&nbsp; 2 |
| Columbia Thermostat Fund<sup>SM</sup> | 900000 | &nbsp;&nbsp;&nbsp;&nbsp;5.39 | &nbsp;&nbsp;&nbsp;&nbsp; 4 |
| Columbia Acorn European Fund<sup>SM</sup> | 200000 | &nbsp;&nbsp;&nbsp;&nbsp;5.25 | &nbsp;&nbsp;&nbsp;&nbsp; 6 |

---

Columbia Acorn Trust \| 2025

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Notes to Financial Statements (continued)

December 31, 2025

Interest expense incurred by the Funds is recorded as Line of credit interest in the Statement of Operations. Columbia Acorn International<sup>®</sup>, Columbia Acorn International Select<sup>SM</sup>, Columbia Thermostat Fund<sup>SM</sup> and Columbia Acorn European Fund<sup>SM</sup> had no outstanding borrowings at December 31, 2025.

Note 8. Risks and uncertainties

An investment in the Funds involve risks, including market risk and concentration risk, among others. The value of each Fund's holdings and each Fund's net asset value may go down. These declines may be due to factors affecting a particular issuer, or the result of, among other things, political, regulatory, market, economic or social developments affecting the relevant market(s) more generally.

Global economies and financial markets are increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market. These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies worldwide. As a result, local, regional or global events such as terrorism, war, other conflicts, natural disasters, disease/virus outbreaks and epidemics or other public health issues, recessions, depressions or other events – or the potential for such events – could have a significant negative impact on global economic and market conditions.

To the extent that each Fund concentrates its investment in particular issuers, countries, geographic regions, industries or sectors, each Fund may be subject to greater risks of adverse developments in such areas of focus than a fund that invests in a wider variety of issuers, countries, geographic regions, industries, sectors or investments.

Additional risk factors of each Fund are described more fully in the Fund's Prospectus and Statement of Additional Information.

**Shareholder concentration risk**

At December 31, 2025, certain shareholder accounts owned more than 20% of the outstanding shares of one or more of the Funds. For unaffiliated shareholder accounts, the Funds have no knowledge about whether any portion of those shares were owned beneficially. Fund shares sold to or redeemed by these accounts may have a significant effect on the operations of the Funds. In the case of a large redemption, the Fund may be forced to sell investments at inopportune times, including its liquid positions, which may result in Fund losses and the Fund holding a higher percentage of less liquid positions. Large redemptions could result in decreased economies of scale and increased operating expenses for non-redeeming Fund shareholders.

The number of accounts and aggregate percentages of shares outstanding held therein were as follows:

---

| | |
|:---|:---|
| **Fund**  | **Percentage of** <br>**shares** <br>**outstanding** <br>**held —** <br>**affiliated (%)**<br>|
| Columbia Acorn<sup>®</sup> Fund |  |
| Columbia Acorn International<sup>®</sup> |  |
| Columbia Acorn International Select<sup>SM</sup> | 26.1 |
| Columbia Thermostat Fund<sup>SM</sup> | 22.6 |
| Columbia Acorn European Fund<sup>SM</sup> | 33.5 |

---

Note 9. Subsequent events

Management has evaluated the events and transactions that have occurred through the date the financial statements were issued and noted no items requiring adjustment of the financial statements or additional disclosure.

Columbia Acorn Trust \| 2025

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Notes to Financial Statements (continued)

December 31, 2025

Note 10. Information regarding pending and settled legal proceedings

Ameriprise Financial and certain of its affiliates are involved, in the normal course of business, in legal proceedings that include regulatory inquiries, arbitration and litigation (including class actions) concerning matters arising in connection with the conduct of their activities as part of a diversified financial services firm. Ameriprise Financial believes that the Funds are not currently the subject of, and that neither Ameriprise Financial nor any of its affiliates are the subject of, any pending legal, arbitration or regulatory proceedings that are likely to have a material adverse effect on the Funds or the ability of Ameriprise Financial or its affiliates to perform under their contracts with the Funds. Ameriprise Financial is required to make quarterly (10-Q), annual (10-K) and, as necessary, 8-K filings with the Securities and Exchange Commission (SEC) on legal and regulatory matters that relate to Ameriprise Financial and its affiliates. Copies of these filings may be obtained by accessing the SEC website at www.sec.gov.

There can be no assurance that these matters, or the adverse publicity associated with them, will not result in increased Fund redemptions, reduced sale of Fund shares or other adverse consequences to the Funds. Further, although we believe proceedings are not likely to have a material adverse effect on the Funds or the ability of Ameriprise Financial or its affiliates to perform under their contracts with the Funds, these proceedings are subject to uncertainties and, as such, it is inherently difficult to determine whether any loss is probable or even reasonably possible, or to reasonably estimate the amount of any loss that may result from such matters. An adverse outcome in one or more of these proceedings could result in adverse judgments, settlements, fines, penalties or other relief, and may lead to further claims, examinations, adverse publicity or reputational damage, each of which could have a material adverse effect on the consolidated financial condition or results of operations or financial condition of Ameriprise Financial or one or more of its affiliates that provide services to the Funds.

Columbia Acorn Trust \| 2025

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Report of Independent Registered Public Accounting Firm

**To the Board of Trustees of Columbia Acorn Trust and Shareholders of Columbia Acorn Fund, Columbia Acorn International, Columbia Acorn International Select, Columbia Thermostat Fund and Columbia Acorn European Fund** 

***Opinions on the Financial Statements***

We have audited the accompanying statements of assets and liabilities, including the portfolios of investments, of Columbia Acorn Fund, Columbia Acorn International, Columbia Acorn International Select, Columbia Thermostat Fund and Columbia Acorn European Fund (constituting Columbia Acorn Trust, hereafter collectively referred to as the "Funds") as of December 31, 2025, the related statements of operations for the year ended December 31, 2025, the statements of changes in net assets for each of the two years in the period ended December 31, 2025, including the related notes, and the financial highlights for each of the periods indicated therein (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of each of the Funds as of December 31, 2025, the results of each of their operations for the year then ended, the changes in each of their net assets for each of the two years in the period ended December 31, 2025 and each of the financial highlights for each of the periods indicated therein in conformity with accounting principles generally accepted in the United States of America.

***Basis for Opinions***

These financial statements are the responsibility of the Funds' management. Our responsibility is to express an opinion on the Funds' financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Funds in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits of these financial statements in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our procedures included confirmation of securities owned as of December 31, 2025 by correspondence with the custodian, transfer agent, issuer of a privately offered security and broker; when replies were not received from the broker, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinions.

/s/PricewaterhouseCoopers LLP

Minneapolis, Minnesota

February 23, 2026

We have served as the auditor of one or more investment companies in the Columbia Funds Complex since 1977.

Columbia Acorn Trust \| 2025

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Federal Income Tax Information

(Unaudited)

The Funds hereby designate the following tax attributes for the fiscal year ended December 31, 2025. Shareholders were notified in early 2026 of the amounts for use in preparing 2025 income tax returns.

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
|  | **Qualified** <br>**dividend** <br>**income**<br>| **Dividends** <br>**received** <br>**deduction**<br>| **Capital** <br>**gain** <br>**dividend**<br>| **Foreign** <br>**taxes paid** <br>**to foreign** <br>**countries**<br>| **Foreign** <br>**taxes paid** <br>**per share** <br>**to foreign** <br>**countries**<br>| **Foreign** <br>**source** <br>**income**<br>| **Foreign** <br>**source** <br>**income** <br>**per share**<br>|
| Columbia Acorn<sup>®</sup> Fund | 0.00% | &nbsp;&nbsp; 0.00% | &nbsp;&nbsp; $26612403 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 |
| Columbia Acorn International<sup>®</sup> | 100.00% | &nbsp;&nbsp; 0.00% | &nbsp;&nbsp; $25055753 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 | &nbsp;&nbsp; $17540885 | &nbsp;&nbsp; $0.5007 |
| Columbia Acorn International Select<sup>SM</sup> | 65.38% | &nbsp;&nbsp; 0.00% | &nbsp;&nbsp; $945272 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 | &nbsp;&nbsp; $4621843 | &nbsp;&nbsp; $0.6636 |
| Columbia Thermostat Fund<sup>SM</sup> | 8.13% | &nbsp;&nbsp; 7.80% | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 | &nbsp;&nbsp; $0 | &nbsp;&nbsp; $0.0000 |
| Columbia Acorn European Fund<sup>SM</sup> | 100.00% | &nbsp;&nbsp; 0.00% | &nbsp;&nbsp; $6167507 | &nbsp;&nbsp; $86162 | &nbsp;&nbsp; $0.0574 | &nbsp;&nbsp; $1053336 | &nbsp;&nbsp; $0.7017 |

---

**Qualified dividend income.** For taxable, non-corporate shareholders, the percentage of ordinary income distributed during the fiscal year that represents qualified dividend income subject to reduced tax rates.

**Dividends received deduction.** The percentage of ordinary income distributed during the fiscal year that qualifies for the corporate dividends received deduction.

**Capital gain dividend.** The Fund designates as a capital gain dividend the amount reflected above, or if subsequently determined to be different, the net capital gain of such fiscal period.

**Foreign taxes.** The Fund makes the election to pass through to shareholders the foreign taxes paid. Eligible shareholders may claim a foreign tax credit. These taxes, and the corresponding foreign source income, are provided in the table above.

Columbia Acorn Trust \| 2025

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Results of Meeting of Shareholders

(Unaudited)

At a Joint Special Meeting of Shareholders held on February 26, 2025, shareholders of Columbia Acorn Trust elected each of the fifteen nominees for trustee to the Board of Trustees of Columbia Acorn Trust, each to hold office until he or she dies, retires, resigns or is removed or, if sooner, until the election and qualification of his or her successor, as follows:

---

| | | | |
|:---|:---|:---|:---|
| **Trustee** | **Votes for** | **Votes withheld** | **Abstentions** |
| George S. Batejan | &nbsp;&nbsp;&nbsp;&nbsp; 205615145 | &nbsp;&nbsp;&nbsp;&nbsp; 14931583 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Daniel J. Beckman | &nbsp;&nbsp;&nbsp;&nbsp; 203656312 | &nbsp;&nbsp;&nbsp;&nbsp; 16890417 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Kathleen Blatz | &nbsp;&nbsp;&nbsp;&nbsp; 205888392 | &nbsp;&nbsp;&nbsp;&nbsp; 14658336 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Pamela G. Carlton | &nbsp;&nbsp;&nbsp;&nbsp; 205814242 | &nbsp;&nbsp;&nbsp;&nbsp; 14732486 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Janet Langford Carrig | &nbsp;&nbsp;&nbsp;&nbsp; 205925510 | &nbsp;&nbsp;&nbsp;&nbsp; 14621219 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| J. Kevin Connaughton | &nbsp;&nbsp;&nbsp;&nbsp; 206197272 | &nbsp;&nbsp;&nbsp;&nbsp; 14349457 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Olive M. Darragh | &nbsp;&nbsp;&nbsp;&nbsp; 206757668 | &nbsp;&nbsp;&nbsp;&nbsp; 13789060 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Patricia M. Flynn | &nbsp;&nbsp;&nbsp;&nbsp; 205709045 | &nbsp;&nbsp;&nbsp;&nbsp; 14837684 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Brian J. Gallagher | &nbsp;&nbsp;&nbsp;&nbsp; 205784907 | &nbsp;&nbsp;&nbsp;&nbsp; 14761821 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Douglas A. Hacker | &nbsp;&nbsp;&nbsp;&nbsp; 204217674 | &nbsp;&nbsp;&nbsp;&nbsp; 16329055 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Nancy T. Lukitsh | &nbsp;&nbsp;&nbsp;&nbsp; 203953914 | &nbsp;&nbsp;&nbsp;&nbsp; 16592814 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| David M. Moffett | &nbsp;&nbsp;&nbsp;&nbsp; 201809833 | &nbsp;&nbsp;&nbsp;&nbsp; 18736895 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Catherine James Paglia | &nbsp;&nbsp;&nbsp;&nbsp; 203734401 | &nbsp;&nbsp;&nbsp;&nbsp; 16812327 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Natalie A. Trunow | &nbsp;&nbsp;&nbsp;&nbsp; 204536248 | &nbsp;&nbsp;&nbsp;&nbsp; 16010480 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |
| Sandra L. Yeager | &nbsp;&nbsp;&nbsp;&nbsp; 204737943 | &nbsp;&nbsp;&nbsp;&nbsp; 15808786 | &nbsp;&nbsp;&nbsp;&nbsp; 0 |

---

Columbia Acorn Trust \| 2025

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P.O. Box 219104

Kansas City, MO 64121-9104

![](g38195imge99b32b42.jpg)

**Please read and consider the investment objectives, risks, charges and expenses for any fund carefully before investing. For a prospectus and summary prospectus, which contains this and other important information about the Funds, go to** 

columbiathreadneedleus.com/investor/**.** The Funds are distributed by Columbia Management Investment Distributors, Inc., member FINRA, and managed by Columbia Management Investment Advisers, LLC.

Columbia Threadneedle Investments<sup>®</sup> (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies. All rights reserved.© 2026 Columbia Management Investment Advisers, LLC.

columbiathreadneedleus.com/investor/

ANN110_12_T01_(02/26)

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#### Item 8. Changes in and Disagreements with Accountants for Open-End Management Investment Companies.
Not applicable.

#### Item 9. Proxy Disclosures for Open-End Management Investment Companies.
Proxy disclosures for Open-End Management Investment Companies is included in Item 7 of this Form N-CSR.

#### Item 10. Remuneration Paid to Directors, Officers, and Others of Open-End Management Investment Companies.
The fees and expenses of the independent trustees are included in "Compensation of board members" and "Deferred compensation of board members" on each Fund's Statement of Operations as part of the Registrant's financial statements filed under Item 7 of this Form N-CSR. Additionally, the compensation paid by the Trust to the Chief Compliance Officer is included in "Compensation of chief compliance officer" on each Fund's Statement of Operations as part of the Registrant's financial statements filed under Item 7 of this Form N-CSR.

------

#### Item 11. Statement Regarding Basis for Approval of Investment Advisory Contract.
Not applicable.

#### Item 12. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies.
Not applicable.

#### Item 13. Portfolio Managers of Closed-End Management Investment Companies.
Not applicable.

#### Item 14. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.
Not applicable.

#### Item 15. Submission of Matters to a Vote of Security Holders.
There were no material changes to the procedures by which shareholders may recommend nominees to the registrant's board of trustees implemented since the registrant last provided disclosure as to such procedures in response to the requirements of Item 407(c)(2)(iv) of Regulation S-K or Item 15 of Form N-CSR.

#### Item 16. Controls and Procedures.
(a) The registrant's principal executive officer and principal financial officer, based on their evaluation of the registrant's disclosure controls and procedures as of a date within 90 days of the filing of this report, have concluded that such controls and procedures are effective and adequately designed to ensure that information required to be disclosed by the registrant in Form N-CSR is accumulated and communicated to the registrant's management, including the principal executive officer and principal financial officer, or persons performing similar functions, as appropriate to allow timely decisions regarding required disclosure.

(b) There was no change in the registrant's internal control over financial reporting that occurred during the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting.

#### Item 17. Disclosure of Securities Lending Activities for Closed-End Management Investment Companies.
Not applicable.

#### Item 18. Recovery of Erroneously Awarded Compensation.
Not applicable.

------

#### Item 19. Exhibits.

---

| | |
|:---|:---|
| (a)(1) | [Code of ethics required to be disclosed under Item 2 of Form N-CSR attached hereto as Exhibit 99.CODE ETH.](d38195dex99codeeth.htm) |
| (a)(2) | Not applicable. |
| (a)(3) | [Certifications pursuant to Rule 30a-2(a) under the Investment Company Act of 1940 (17 CFR 270.30a-2(a)) attached hereto as Exhibit 99.CERT.](d38195dex99cert.htm) |
| (a)(4) | Not applicable. |
| (a)(5) | Not applicable. |
| (b) | [Certification pursuant to Rule 30a-2(b) under the Investment Company Act of 1940 (17 CFR 270.30a-2(b)) attached hereto as Exhibit 99.906CERT.](d38195dex99906cert.htm) |

---

------

#### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

#### Columbia Acorn Trust

---

| | |
|:---|:---|
| By: | /s/ Michael G. Clarke |
| Name: | Michael G. Clarke |
| Title: | President and Principal Executive Officer |
| Date: | February 23, 2026 |

---

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

---

| | |
|:---|:---|
| By: | /s/ Michael G. Clarke |
| Name: | Michael G. Clarke |
| Title: | President and Principal Executive Officer |
| Date: | February 23, 2026 |
| By: | /s/ Charles H. Chiesa |
| Name: | Charles H. Chiesa |
| Title: | Treasurer, Chief Financial Officer, Chief Accounting Officer and Principal Financial Officer |
| Date: | February 23, 2026 |

---

## Ex-99.Code

**Exhibit 99.CODE ETH.** 

**COLUMBIA FUNDS** 

---

| | |
|:---|:---|
| **Applicable Regulatory Authority** | Section 406 of the Sarbanes-Oxley Act of 2002; Item 2 of Form N-CSR |
| **Related Policies** | Overview and Implementation of Compliance Program Policy |
| **Requires Annual Board Approval** | No but Covered Officers Must provide annual certification |
| **Last Reviewed by AMC** | September 2025 |

---

**<u>Overview and Statement</u>**

Item 2 of Form N-CSR, the form used by registered management investment companies to file certified annual and semi-annual shareholder reports, requires a registered management investment company to disclose:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Whether it has adopted a code of ethics that applies to the investment company's principal executive
officer and senior financial officers and, if it has not adopted such a code of ethics, why it has not done so; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Any amendments to, or waivers from, the code of ethics relating to such officers.

The Board of the Columbia Funds ("Columbia Board") has adopted the following Code of Ethics for Principle Executive and Senior Financial Officers (the "Code"), which sets forth the ethical standards to which the Funds holds their principal executive officer and each of its senior financial officers.

This Code should be read and interpreted in conjunction with the *Overview and Implementation of Compliance Program Policy*.

**<u>Policy</u>**

The Board has adopted the Code in order to comply with applicable regulatory requirements as outlined below:

**I.** **Covered Officers/Purpose of the Code** 

This Code applies to the Fund's Principal Executive Officer, Principal Financial Officer, and Principal Accounting Officer or Controller (the "Covered Officers") for the purpose of promoting:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between
personal and professional relationships;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Full, fair, accurate, timely and understandable disclosure in reports and documents that the Fund files with, or
submits to, the SEC, and in other public communications made by the Fund;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Compliance with applicable laws and governmental rules and regulations;

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The prompt internal reporting of violations of the Code to an appropriate person or persons identified in the
Code; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Accountability for adherence to the Code.

Each Covered Officer should adhere to a high standard of business ethics and should be sensitive to situations that may give rise to actual or apparent conflicts of interest.

**II.** **Administration of the Code** 

The Board has designated an individual to be primarily responsible for the administration of the Code (the "Code Officer"). In the absence of the Code Officer, his or her designee shall serve as the Code Officer, but only on a temporary basis.

The Board has designated a person who meets the definition of a Chief Legal Officer (the "CLO") for purposes of the Sarbanes-Oxley Act of 2002 and the rules promulgated thereunder as the Fund's CLO. The CLO of the Fund shall assist the Fund's Code Officer in administration of this Code. The Code Officer, in consultation with the CLO, shall be responsible for applying this Code to specific situations (in consultation with Fund counsel, where appropriate) and has the authority to interpret this Code in any particular situation.

**III.** **Managing Conflicts of Interest** 

A "conflict of interest" occurs when a Covered Officer's personal interest interferes with the interests of, or his or her service to, the Fund. For example, a conflict of interest would arise if a Covered Officer, or a member of his or her family, receives improper personal benefits as a result of the Covered Officer's position with the Fund. Certain provisions in the 1940 Act and the rules and regulations thereunder and the Advisers Act and the rules and regulations thereunder govern certain conflicts of interest that arise out of the relationships between Covered Officers and the Fund. If such conflicts are addressed in conformity with applicable provisions of the 1940 Act and the Advisers Act, they will be deemed to have been handled ethically. The Fund's and its Adviser's compliance programs and procedures are designed to prevent, or identify and correct, violations of those provisions. This Code does not, and is not intended to, repeat or replace those programs and procedures, and conduct that is consistent with such programs and procedures falls outside of the parameters of this Code.

Although they do not typically present an opportunity for improper personal benefit, conflicts may arise from, or as a result of, the contractual relationships between the Fund and, as applicable, its Adviser (Columbia Management Investment Advisers, LLC ("CMIA") for the Columbia Funds, administrator, principal underwriter, pricing and bookkeeping agent and/or transfer agent (each, a "Primary Service Provider") of which the Covered Officers are also officers or employees. As a result, this Code recognizes that the Covered Officers will, in the normal course of their duties (whether formally for the Fund or for a Primary Service Provider, or for both), be involved in establishing policies and implementing decisions that will have different effects on the Primary Service Providers and the Fund. The participation of the Covered Officers in such activities is inherent in the contractual relationships between the Fund and the Primary Service Providers and is consistent with the performance by the Covered Officers of their duties as officers of the Fund. If such conflicts are addressed in conformity with applicable provisions of the 1940 Act and the Advisers Act, they will be deemed to have been handled ethically. In addition, it is recognized by the Board of the Funds that the Covered Officers also may be officers or employees of one or more other investment companies or organizations affiliated with the sponsor of the Funds covered by other similar codes and that the codes of ethics of those other investment companies or organizations will apply to the Covered Officers acting in such capacities for such other investment companies.

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

------

This Code covers general conflicts of interest and other issues applicable to the Funds under the Sarbanes-Oxley Act of 2002. The overarching principle is that the personal interest of a Covered Officer should not be placed improperly before the interests of the Funds. Certain examples of such conflicts of interest follow.

Each Covered Officer must:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Not use his or her personal influence or personal relationships improperly to influence investment decisions or
financial reporting by the Fund whereby the Covered Officer, or a member of his or her family, would knowingly benefit personally to the detriment of the Fund;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Not knowingly cause the Fund to take action, or fail to take action, for the individual personal benefit of the
Covered Officer, or a member of his or her family, rather than the benefit of the Fund;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Not use material non-public knowledge of portfolio transactions made
or contemplated for the Fund to trade personally or cause others to trade personally in contemplation of the market effect of such transactions; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Report at least annually (or more frequently, as appropriate) known affiliations or other relationships that may
give rise to conflicts of interest with respect to the Fund.

If a Covered Officer believes that he or she has a potential conflict of interest that is likely to materially compromise his or her objectivity or his or her ability to perform the duties of his or her role as a Covered Officer, including a potential conflict of interest that arises out of his or her responsibilities as an officer or employee of one or more Primary Service Providers or other funds, he or she should consult with the Code Officer, the CLO, the Fund's outside counsel, or counsel to the Independent Board Members, as appropriate.

Examples of potential conflicts of interest that may materially compromise objectivity or ability to perform the duties of a Covered Officer and which the Covered Officer should consider discussing with the Code Officer or other appropriate person include:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Service as a director on the board of a public or private company or service as a public official;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The receipt of a non-de minimus gift when the gift is in relation to
doing business directly or indirectly with the Fund;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The receipt of entertainment from any company with which the Fund has current or prospective business dealings,
unless such entertainment is business-related, reasonable in cost, appropriate as to time and place, and not so frequent as to raise any question of impropriety;

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• An ownership interest in, or any consulting or employment relationship with, any of the Fund's service
providers, other than the Primary Service Providers or any affiliated person thereof; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• A direct or indirect material financial interest in commissions, transaction charges or spreads paid by the Fund
for effecting portfolio transactions or for selling or redeeming shares other than an interest arising from the Covered Officer's employment, such as compensation or equity ownership.

**IV.** **Disclosure and Compliance** 

It is the responsibility of each Covered Officer:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• To familiarize himself or herself with the disclosure requirements generally applicable to the Fund, as well as
the business and financial operations of the Fund;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• To not knowingly misrepresent, and to not knowingly cause others to misrepresent, facts about the Fund to others,
whether within or outside the Fund, including to the Fund's Board, Legal Counsel, Independent Legal Counsel and auditors, and to governmental regulators and self-regulatory organizations;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• To the extent appropriate within his or her area of responsibility, consult with other officers and employees of
the Fund and the Primary Service Providers with the goal of promoting full, fair, accurate, timely and understandable disclosure in the reports and documents the Fund files with, or submits to, the SEC and in other public communications made by the
Fund; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• To adhere to and, within his or her area of responsibility, promote compliance with the standards and
restrictions imposed by applicable laws, rules and regulations.

**V.** **Reporting and Accountability by Covered Officers** 

Each Covered Officer must:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Upon adoption of the Code or becoming a Covered Officer, acknowledge in writing to the Fund's Board that he
or she has received, read and understands the Code, using the form attached as Appendix A hereto;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Annually thereafter acknowledge in writing to the Fund's Board that he or she has received and read the
Code and believes that he or she has complied with the requirements of the Code, using the form attached as Appendix B hereto;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Not retaliate against any employee or Covered Officer for reports of potential violations that are made in good
faith; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Notify the Code Officer promptly if he or she knows of any violation, or of conduct that reasonably could be
expected to be or result in a violation, of this Code. Failure to do so is a violation of this Code.

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

------

The Fund will follow the policy set forth below in investigating and enforcing this Code:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The Code Officer will endeavor to take all appropriate action to investigate any potential violation reported to
him or her;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If, after such investigation, the Code Officer believes that no violation has occurred, the Code Officer will so
notify the person(s) reporting the potential violation, and no further action is required;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Any matter that the Code Officer, upon consultation with the CLO, believes is a violation will be reported by the
Code Officer or the CLO to the Fund's Audit Committee;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The Fund's Audit Committee will be responsible for granting waivers, as appropriate; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• This Code and any changes to or waivers of the Code will, to the extent required, be disclosed as provided by SEC
rules.

**VI.** **Other Policies** 

This Code shall be the sole code of ethics adopted by the Fund for the purposes of Section 406 of the Sarbanes-Oxley Act of 2002 and the rules and forms applicable to registered management investment companies thereunder. Insofar as other policies or procedures of the Fund or the Fund's Primary Service Providers govern or purport to govern the behavior or activities of the Covered Officers who are subject to this Code, they are superseded by this Code to the extent that they conflict with the provisions of this Code. The Fund's and its Adviser's and principal underwriter's codes of ethics under Rule 17j-1 under the 1940 Act and the more detailed policies and procedures of the Primary Service Providers as set forth in their respect Compliance Manuals are separate requirements applicable to the Covered Officers and are not part of this Code.

**VII.** **Disclosure of Amendments to the Code** 

Any amendments will, to the extent required, be disclosed in accordance with law.

**VIII.** **Confidentiality** 

All reports and records prepared or maintained pursuant to this Code will be considered confidential and shall be maintained and protected accordingly. Except as otherwise required by law or this Code or upon advice of counsel, such reports and records shall not be disclosed to anyone other than the Fund's Board, the Covered Officers, the Code Officer, the CLO, the Fund's Primary Service Providers and their affiliates, and outside audit firms, legal counsel to the Fund and legal counsel to the Independent Board Members.

**IX.** **Internal Use** 

The Code is intended solely for the internal use by the Fund and does not constitute an admission, by or on behalf of the Fund, as to any fact, circumstance, or legal conclusion.

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

------

**Reporting Requirements** 

Each Covered Officer must annually acknowledge in writing to the Fund's Board that he or she has received and read the Code and believes that he or she has complied with the requirements of the Code, using the form attached as Appendix II hereto.

The Code Officer or CLO shall report to the Fund's Audit Committee any violations of, or material issues arising under, this Code.

If the Audit Committee concurs that a violation has occurred, it will inform and make a recommendation to the Fund's Board, which will consider appropriate action, which may include review of, and appropriate modifications to: Applicable policies and procedures; Notification to the appropriate personnel of the Fund's Primary Service Providers or their boards; A recommendation to censure, suspend or dismiss the Covered Officer; or Referral of the matter to the appropriate authorities for civil action or criminal prosecution.

All material amendments to this Code must be in writing and approved or ratified by the Fund's Board, including a majority of the Independent Board Members.

The Code Officer, in conjunction with the CLO, shall be responsible for administration of this Code and for adopting procedures to ensure compliance with the requirements set forth herein.

Any issues that arise under this policy should be communicated to an employee's immediate supervisor, and appropriately escalated to AMC. Additionally, AMC will escalate any compliance issues relating to this Code to the Fund CCO and, if warranted, the appropriate Fund Board.

**Monitoring/Oversight/Escalation** 

The Code Officer shall be responsible for oversight of compliance with this Code by the Covered Officers. AMC and Ameriprise Risk & Control Services may perform periodic reviews and assessments of various lines of business, including their compliance with this Code.

**Recordkeeping** 

All records must be maintained for at least seven years, the first three in the appropriate Ameriprise Financial, Inc. management office. The following records will be maintained to evidence compliance with this Code: (1) a copy of the information or materials supplied to the Audit Committee or the Board: (i) that provided the basis for any amendment or waiver to this Code; and (ii) relating to any violation of the Code and sanctions imposed for such violation, together with a written record of the approval or action taken by the Audit Committee and/or Board; (2) a copy of the policy and any amendments; and (3) a list of Covered Officers and reporting by Covered Officers.

*This document is current as of the last review date but subject to change thereafter. Please consult the online version to verify that this Fund Policy has not been updated or otherwise changed. This Fund Policy is the property of the Funds and must not be provided to any external party without express prior consent from the Fund CCO.*

*Proprietary and Confidential*

## Ex-99.Cert

**EX-99.CERT SECTION 302 CERTIFICATION** 

I, Michael G. Clarke, certify that:

1. I have reviewed this report on Form N-CSR of Columbia Acorn Trust;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be
designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is
being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) designed such internal control over financial reporting, or caused such internal control over financial
reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting
principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c) evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this
report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d) disclosed in this report any change in the registrant's internal control over financial reporting that
occurred during the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer(s) and I have disclosed to the registrant's auditors and the audit committee of the registrant's board of trustees (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) all significant deficiencies and material weaknesses in the design or operation of internal control over
financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize, and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) any fraud, whether or not material, that involves management or other employees who have a significant role in
the registrant's internal control over financial reporting.

------

---

| | |
|:---|:---|
| By: | /s/ Michael G. Clarke |
| Name: | Michael G. Clarke |
| Title: | President and Principal Executive Officer |
| Date: | February 23, 2026 |

---

------

I, Charles H. Chiesa, certify that:

1. I have reviewed this report on Form N-CSR of Columbia Acorn Trust;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be
designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is
being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(f) designed such internal control over financial reporting, or caused such internal control over financial
reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting
principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(g) evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this
report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(h) disclosed in this report any change in the registrant's internal control over financial reporting that
occurred during the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer(s) and I have disclosed to the registrant's auditors and the audit committee of the registrant's board of trustees (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c) all significant deficiencies and material weaknesses in the design or operation of internal control over
financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize, and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d) any fraud, whether or not material, that involves management or other employees who have a significant role in
the registrant's internal control over financial reporting.

------

---

| | |
|:---|:---|
| By: | /s/ Charles H. Chiesa |
| Name: | Charles H. Chiesa |
| Title: | Treasurer, Chief Financial Officer, Chief Accounting Officer and Principal Financial Officer |
| Date: | February 23, 2026 |

---

## Exhibit 99.906

**EX-99.906 CERT SECTION 906 CERTIFICATION** 

**CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002** 

In connection with the Certified Shareholder Report of Columbia Acorn Trust (the "Trust") on Form N-CSR for the period ending December 31, 2025 as filed with the Securities and Exchange Commission on the date hereof ("the Report"), the undersigned hereby certifies that, to his knowledge:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Trust.

---

| | |
|:---|:---|
| By: | /s/ Michael G. Clarke |
| Name: | Michael G. Clarke |
| Title: | President and Principal Executive Officer |
| Date: | February 23, 2026 |
| By: | /s/ Charles H. Chiesa |
| Name: | Charles H. Chiesa |
| Title: | Treasurer, Chief Financial Officer, Chief Accounting Officer and Principal Financial Officer |
| Date: | February 23, 2026 |

---

A signed original of this written statement required by Section 906 of the Sarbanes-Oxley Act of 2002 has been provided to the Registrant and will be retained by the Registrant and furnished to the Securities and Exchange Commission (the "Commission") or its staff upon request.

This certification is being furnished to the Commission solely pursuant to 18 U.S.C. §1350 and is not being filed as part of the Form N-CSR with the Commission.