# EDGAR Filing Document

**Accession Number:** 0000732337
**File Stem:** 0001193125-25-259887
**Filing Date:** 2025-10
**Character Count:** 2655
**Document Hash:** 81d348c9baf6d2d6ad72a21b35bfcdb6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-259887.hdr.sgml**: 20251031

**ACCESSION NUMBER**: 0001193125-25-259887

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20251031

**DATE AS OF CHANGE**: 20251031

**EFFECTIVENESS DATE**: 20251031

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** PUTNAM MORTGAGE SECURITIES FUND
- **CENTRAL INDEX KEY:** 0000732337

**ORGANIZATION NAME:**
- **EIN:** 042811119
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 0930

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 002-87634
- **FILM NUMBER:** 251438367

**BUSINESS ADDRESS:**
- **STREET 1:** 100 FEDERAL STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02110
- **BUSINESS PHONE:** 6172921000

**MAIL ADDRESS:**
- **STREET 1:** 100 FEDERAL STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02110

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PUTNAM U S GOVERNMENT INCOME TRUST
- **DATE OF NAME CHANGE:** 19920703

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PUTNAM U S GOVERNMENT GUARANTEED SECURITIES INCOME TRUST
- **DATE OF NAME CHANGE:** 19910102

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PUTNAM UNITED STATES GOVERNMENT SECURITIES INCOME FUND
- **DATE OF NAME CHANGE:** 19840806

## Series and Classes Contracts Data

### PUTNAM MORTGAGE SECURITIES FUND (Series ID: S000006570)

| Class ID   | Class Name      | Ticker Symbol   |
|:---|:---|:---|
| C000017922 | Class A Shares  | PGSIX           |
| C000017924 | Class C Shares  | PGVCX           |
| C000017926 | Class R Shares  | PGVRX           |
| C000017927 | Class Y Shares  | PUSYX           |
| C000200295 | Class R6 Shares |  |

PGOF-P41

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ![LOGO](g922790g01v01.jpg)

**SUPPLEMENT DATED OCTOBER 31, 2025** 

**TO THE SUMMARY PROSPECTUS, PROSPECTUS** 

**AND STATEMENT OF ADDITIONAL INFORMATION ("SAI")** 

**OF EACH FUND LISTED IN SCHEDULE A** 

**Effective October 31, 2025, the following changes are made to each fund's Summary Prospectus, Prospectus and SAI:** 

**a)** **The following footnote is added to all references to Paul Varunok in each fund's Summary Prospectus, Prospectus and SAI:** 

\* Mr. Varunok is anticipated to step down as a member of the fund's portfolio management team on or about December 31, 2025. Thereafter, he will transition to an advisory role with Franklin Templeton.

**<u>Schedule A</u>**

---

| |
|:---|
|  Putnam Mortgage Securities Fund |
|  Putnam Mortgage Opportunities Fund |
|  Putnam VT Mortgage Securities Fund |

---

*Shareholders should retain this Supplement for future reference.*