# EDGAR Filing Document

**Accession Number:** 0000822632
**File Stem:** 0001193125-26-069352
**Filing Date:** 2026-2
**Character Count:** 6716
**Document Hash:** 9a20251e0400b7a4793a08825d48d817
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-069352.hdr.sgml**: 20260225

**ACCESSION NUMBER**: 0001193125-26-069352

**CONFORMED SUBMISSION TYPE**: 485BXT

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260225

**DATE AS OF CHANGE**: 20260225

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** WILLIAM BLAIR FUNDS
- **CENTRAL INDEX KEY:** 0000822632

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 485BXT
- **SEC ACT:** 1940 Act
- **SEC FILE NUMBER:** 811-05344
- **FILM NUMBER:** 26675293

**BUSINESS ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606
- **BUSINESS PHONE:** 3123648000

**MAIL ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** WILLIAM BLAIR MUTUAL FUNDS INC
- **DATE OF NAME CHANGE:** 19960112

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** BLAIR WILLIAM READY RESERVES INC
- **DATE OF NAME CHANGE:** 19920316
**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** WILLIAM BLAIR FUNDS
- **CENTRAL INDEX KEY:** 0000822632

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 485BXT
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 033-17463
- **FILM NUMBER:** 26675292

**BUSINESS ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606
- **BUSINESS PHONE:** 3123648000

**MAIL ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** WILLIAM BLAIR MUTUAL FUNDS INC
- **DATE OF NAME CHANGE:** 19960112

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** BLAIR WILLIAM READY RESERVES INC
- **DATE OF NAME CHANGE:** 19920316

## Series and Classes Contracts Data

### William Blair Global Leaders Fund (Series ID: S000019315)

| Class ID   | Class Name   | Ticker Symbol   |
|:---|:---|:---|
| C000053607 | Class N      | WGGNX           |
| C000053608 | Class I      | WGFIX           |
| C000053609 | Class R6     | BGGIX           |

**As filed with the Securities and Exchange Commission on or about February 25, 2026** 

**Registration No. 033-17463 and 811-05344** 

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

**FORM N-1A** 

**REGISTRATION STATEMENT** 

***UNDER***

---

| | |
|:---|:---|
| ***THE SECURITIES ACT OF 1933*** | ☒ |
| **Pre-Effective Amendment No.** | ☐ |
| **Post-Effective Amendment No. 158** | ☒ |

---

**and** 

**REGISTRATION STATEMENT** 

***UNDER***

---

| | |
|:---|:---|
| ***THE INVESTMENT COMPANY ACT OF 1940*** | ☒ |
| **Amendment No. 159** | ☒ |

---

## WILLIAM BLAIR FUNDS
**(Exact Name of Registrant as Specified in Charter)** 

**150 North Riverside Plaza Chicago, Illinois 60606** 

**(Address of Principal Executive Offices, including Zip Code)** 

**Registrant's Telephone Number, Including Area Code: (312) 364-8000** 

---

| | |
|:---|:---|
| **(Name and Address of Agent for Service)**<br>**Lisa Rusch**<br> **William Blair Investment Management, LLC**<br> **150 North Riverside Plaza**<br> **Chicago, Illinois 60606** | ***Copy to:***<br>**Allison M. Fumai, Esq.**<br> **Stephanie A. Capistron, Esq.**<br> **Dechert LLP**<br> **One International Place, 40<sup>th</sup> Floor**<br> **100 Oliver Street**<br> **Boston, Massachusetts 02110** |

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It is proposed that this filing will become effective (check appropriate box)

☐ immediately upon filing pursuant to paragraph (b)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;☒ on <u> </u> March 5, 2026, pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ on<u> </u> , pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ on<u> </u>, pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;☒ this post-effective amendment designates a new effective date for a previously filed post-effective amendment.

Approximate Date of Proposed Public Offering: As soon as practicable after the effective date of the registration statement

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**<u>EXPLANATORY NOTE</u>**

The purpose of this filing is to delay the effectiveness of the Registrant's Post-Effective Amendment No. 156 under the Securities Act of 1933 ("PEA 156") to its Registration Statement until March 5, 2026. [Parts A, B, and C of the Registrant's PEA 156 filed on November 28, 2025 are incorporated by reference herein.](http://www.sec.gov/Archives/edgar/data/822632/000119312525302233/d27992d485apos.htm) The effectiveness of PEA 156 was previously delayed by the Registrant's Post Effective Amendment No. 157 under the Securities Act of 1933 which was filed on January 26, 2026.

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**SIGNATURES** 

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for effectiveness of this registration statement under Rule 485(b) under the Securities Act of 1933 and that it has duly caused this Post-Effective Amendment No. 158 to the registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Chicago, and State of Illinois, on the 25th day of February, 2026.

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| | |
|:---|:---|
| WILLIAM BLAIR FUNDS | WILLIAM BLAIR FUNDS |
| By: | /s/ Lisa Rusch |
|  | Lisa Rusch, President |

---

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment No. 158 to the registration statement has been signed below by the following persons in the capacity indicated on the 25th day of February, 2026.

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| | |
|:---|:---|
|  **Signature** | **Title** |
|  /s/ Lisa Rusch<br> Lisa Rusch | President (Principal Executive Officer) |
|  /s/ Cissie Citardi\*<br> Cissie Citardi | Trustee |
|  /s/ Vann A. Avedisian\*<br> Vann A. Avedisian | Trustee |
|  /s/ Kathleen T. Barr\*<br> Kathleen T. Barr | Trustee |
|  /s/ Michelle E. Borré Massick\*<br> Michelle E. Borré Massick | Trustee |
|  /s/ Daniel N. Leib\*<br> Daniel N. Leib | Trustee |
|  /s/ Dorri C. McWhorter\*<br> Dorri C. McWhorter | Trustee |
|  /s/ Steven R. Zenz\*<br> Steven R. Zenz | Trustee |
| /s/ John M. Raczek<br> John M. Raczek | Treasurer (Principal Financial Officer, Principal Accounting Officer) |

---

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| | |
|:---|:---|
|  \*By: | /s/ Lisa Rusch |
|  | Lisa Rusch, Attorney-in-Fact |

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\* Lisa Rusch signs this document pursuant to powers of attorney filed as an exhibit to Post-Effective Amendment No. 156.