Prospectus by Investment Company (Form 497)

MASSMUTUAL FUNDS

MassMutual Small Cap Opportunities Fund

Supplement dated October 6, 2026 to the

Prospectus dated February 1, 2026 and the

Summary Prospectus dated February 1, 2026

This supplement provides new and additional information beyond that contained in the Prospectus and Summary Prospectus, and any previous supplements. It should be retained and read in conjunction with the Prospectus and Summary Prospectus, and any previous supplements.

Effective immediately, the information for Joy Budzinski, Magnus Krantz, and Raman Vardharaj found (on page 34 of the Prospectus) under the heading Portfolio Manager(s) in the section titled Management and on pages 64 and 65 of the Prospectus under the heading Subadvisers and Portfolio Managers in the section titled Management of the Funds, is hereby removed.

Effective immediately, the following information supplements the information found under the heading Portfolio Manager(s) in the section titled Management (on page 34 of the Prospectus):

Bryan Lassiter, CFA is a Portfolio Manager at Invesco Advisers. He has managed the Fund since September 2026.

Effective immediately, the following information supplements the information for Invesco Advisers, Inc. beginning on page 64 of the Prospectus under the heading Subadvisers and Portfolio Managers in the section titled Management of the Funds:

Bryan Lassiter, CFA 

is a portfolio manager of the MassMutual Small Cap Opportunities Fund. Mr. Lassiter is a Portfolio Manager at Invesco Advisers. He has been associated with Invesco Advisers and/or its affiliates since September 2026. Prior to joining Invesco Advisers, he was a portfolio manager at Columbia Threadneedle from November 2021 to September 2026. Before that, he spent ten years as a senior research analyst at LMCG Investments focused on small- and mid-cap U.S. equities and held earlier research roles at Colebury Capital and Globalt Investments.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

PREMPRO-26-05

SCO-26-01

MASSMUTUAL FUNDS

MassMutual Small Cap Opportunities Fund

Supplement dated October 6, 2026 to the

Statement of Additional Information dated February 1, 2026

This supplement provides new and additional information beyond that contained in the Statement of Additional Information ("SAI") and any previous supplements. It should be retained and read in conjunction with the SAI and any previous supplements.

Effective immediately, the following information replaces similar information for the MassMutual Small Cap Opportunities Fund (the "Fund") found under Invesco Advisers, Inc. on page B-133 in the section titled Appendix C - Additional Portfolio Manager Information: 

The portfolio managers of the Small Cap Opportunities Fund are Bryan Lassiter, Adam Weiner, and Matthew P. Ziehl.

Effective immediately, the following information supplements the information for the Fund found on page B-133 under the headings Other Accounts Managed and Ownership of Securities in the section titled Appendix C - Additional Portfolio Manager Information:

Other Accounts Managed:

Ownership of Securities:

As of June 30, 2026, Mr. Lassiter did not own any shares of the Small Cap Opportunities Fund.

Effective immediately, the information for Joy Budzinski, Magnus Krantz, and Raman Vardharaj found on page B-133 relating to the Fund in the section titled Appendix C - Additional Portfolio Manager Information is hereby removed.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

PREMSAI-26-07