Summary Prospectus by Investment Company (Form 497K)

MML SERIES INVESTMENT FUND

MML Mid Cap Growth Fund

(the "Fund")

Supplement dated November 14, 2025 to the

Prospectus dated April 25, 2025 and the

Summary Prospectus dated April 25, 2025

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.

The following expense limitation information for the Fund is hereby added under the heading Additional Information Regarding Investment Objectives and Principal Investment Strategies (on page 95 of the Prospectus):

MML Mid Cap Growth Fund.

MML Advisers has agreed to cap the fees and expenses of the Fund (other than extraordinary legal and other expenses, Acquired Fund Fees and Expenses, interest expense, expenses related to borrowings, securities lending, leverage, taxes, and brokerage, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses, as applicable) through April 30, 2028, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed 0.83% and 1.08% for Initial Class shares and Service Class shares, respectively. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

MMLPRO-25-07

MMLMCG-25-01