Prospectus by Investment Company (Form 497)

MML SERIES INVESTMENT FUND

MML Managed Volatility Fund

(the "Fund")

Supplement dated February 6, 2026 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 Board of Trustees of the MML Series Investment Fund is expected to approve changes to the Fund at its meeting on March 31-April 1, 2026. If the Board of Trustees approves the changes, the changes described below will take effect on April 24, 2026.

J.P. Morgan Investment Management Inc.("J.P. Morgan") will replace Gateway Investment Advisers, LLC("Gateway") as subadviser of the Fund.

The Fund's name will be changed to the MML VIP JPMorgan U.S. Research Enhanced Equity Fund.

The following information will replace the information for the Fund found in the section titled Investment Objective(on page 51 of the Prospectus):

The Fund seeks to provide a consistently high total return from a broadly diversified portfolio of equity securities with risk characteristics similar to the S&P 500^® Index*.

* The "S&P 500 Index" is a product of S&P Dow Jones Indices LLC or its affiliates ("SPDJI"), and has been licensed for use by MassMutual. S&P^®, S&P 500^®, SPX^®, SPY^®, US 500™, The 500™, iBoxx^®, iTraxx^® and CDX^® are trademarks of S&P Global, Inc. or its affiliates ("S&P"); Dow Jones^® is a registered trademark of Dow Jones Trademark Holdings LLC ("Dow Jones"); and these trademarks have been licensed for use by SPDJI and sublicensed for certain purposes by MassMutual. The Fund is not sponsored, endorsed, sold or promoted by SPDJI, Dow Jones, S&P, or their respective affiliates, and none of such parties make any representation regarding the advisability of investing in such product(s) nor do they have any liability for any errors, omissions, or interruptions of the S&P 500 Index.

The following information will replace the information for the Fund found under the heading Principal Investment Strategiesin the section titled Investments, Risks, and Performance(on pages 51-52 of the Prospectus):

Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of U.S. companies. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stocks, real estate investment trusts ("REITs"), rights, and warrants. The Fund primarily invests in the common stocks of U.S. companies in the S&P 500 Index (the "Index"). The Fund may also invest in securities not included within the Index. As of December 31, 2025, the market capitalization range of companies included in the Index was $5.54 billion to $4.53 trillion. Sector by sector, the Fund's weightings are similar to those of the Index. Within each sector, the Fund's subadviser, J.P. Morgan Investment Management Inc. ("J.P. Morgan"), modestly overweights equity securities that it considers undervalued or fairly valued while modestly underweighting or not holding equity securities that appear overvalued. By owning a large number of equity securities within the Index, with an emphasis on those that appear undervalued or fairly valued, the Fund seeks returns that modestly exceed those of the Index over the long term with a modest level of volatility as compared to the Index.

The Fund may use derivatives as substitutes for securities in which the Fund can invest. To the extent the Fund uses derivatives, the Fund will primarily use futures contracts to more effectively gain targeted equity exposure from its cash positions. Use of derivatives by the Fund may create investment leverage.

In managing the investments of the Fund, J.P. Morgan employs a three-step process that combines research, valuation, and stock selection. J.P. Morgan takes an in-depth look at company prospects, which is designed to provide insight into a company's real growth potential. The research findings allow J.P. Morgan to rank the companies in each sector group according to their relative values.

J.P. Morgan buys and sells equity securities, using the research and valuation rankings as a basis. Along with attractive valuation, J.P. Morgan often considers a number of other criteria:

J.P. Morgan may sell a security as its valuation or ranking changes or if more attractive investments become available.

The following risks will be added under the heading Principal Risks (beginning on page 52 of the Prospectus):

Derivatives Risk Derivatives can be highly volatile and involve risks different from, and potentially greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage. Losses from derivatives can be substantially greater than the derivatives' original cost and can sometimes be unlimited. If the value of a derivative does not correlate well with the particular market or asset class the derivative is designed to provide exposure to, the derivative may not have the effect or benefit anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Many derivatives are traded in the over-the-counter market and not on exchanges.

Foreign Investment Risk; Emerging Markets Risk; Currency RiskInvestments in securities of foreign issuers, securities of companies with significant foreign exposure, and foreign currencies can involve additional risks relating to market, industry, political, regulatory, public health, and other conditions. Political, social, diplomatic, and economic developments, U.S. and foreign government action, or threat thereof, such as the imposition of currency or capital blockages, controls, or tariffs, economic and trade sanctions or embargoes, security trading suspensions, entering or exiting trade or other intergovernmental agreements, or the expropriation or nationalization of assets in a particular country, can cause dramatic declines in certain or all securities with exposure to that country and other countries. Sanctions, or the threat of sanctions, and other trade disputes may cause volatility in regional and global markets and may negatively impact the performance of various sectors and industries, as well as companies in other countries, which could have a negative effect on the performance of the Fund. In the event of nationalization, expropriation, confiscation, or other government action, intervention, or restriction, the Fund could lose its entire investment in a particular foreign issuer or country. There may be quotas or other limits on the ability of the Fund (or clients of the Fund's investment adviser or  subadviser) to invest or maintain investments in securities of issuers in certain countries. Enforcing legal rights can be more difficult, costly, and limited in certain foreign countries and with respect to certain types of investments, and can be particularly difficult against foreign governments. Because non-U.S. securities are normally denominated and traded in currencies other than the U.S. dollar, the value of the Fund's assets may be affected favorably or unfavorably by changes in currency exchange rates, exchange control regulations, and restrictions or prohibitions on the repatriation of non-U.S. currencies. Income and gains with respect to investments in certain countries may be subject to withholding and other taxes. There may be less information publicly available about a non-U.S. company than about a U.S. company, and many non-U.S. companies are not subject to accounting, auditing, and financial reporting standards, regulatory framework and practices comparable to those in the U.S. The securities of some non-U.S. companies, especially those in emerging markets, are less liquid and at times more volatile than securities of comparable U.S. companies. Emerging markets securities are subject to greater risks than securities issued in developed foreign markets, including less liquidity, less stringent investor protection and disclosure standards, less reliable settlement practices, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody and operational risks, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater volatility in currency exchange rates, and are more susceptible to environmental problems. Many emerging market countries are highly reliant on international trade and exports, including the export of commodities. Their economies may be significantly impacted by fluctuations in commodity prices and the global demand for certain commodities. In addition, pandemics and outbreaks of contagious diseases may exacerbate pre-existing problems in emerging market countries with less established health care systems. Frontier markets, a subset of emerging markets, generally have smaller economies and less mature capital markets than emerging markets. As a result, the risks of investing in emerging market countries are magnified in frontier market countries. Frontier markets are more susceptible to having abrupt changes in currency values, less mature markets and settlement practices, and lower trading volumes that could lead to greater price volatility and illiquidity. Non-U.S. transaction costs, such as brokerage commissions and custody costs, may be higher than in the United States. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, public health, and other conditions than the U.S. market. The Fund may invest in foreign securities known as depositary receipts. Investments in depositary receipts are subject to the same risks as direct investment in foreign securities, which include market, political, currency, and regulatory risks.

Indexing RiskThe Fund's performance may not track the performance of the index due to a number of factors, including fees and expenses of the Fund, the Fund's cash positions, and differences between securities held by the Fund and the securities comprising the index which may result from legal restrictions, costs, or liquidity constraints, especially during times when a sampling methodology is used.

Liquidity RiskCertain securities may be difficult (or impossible) to sell or certain positions may be difficult to close out at a desirable time and price, and the Fund may be required to hold an illiquid investment that is declining in value, or it may be required to sell certain illiquid investments at a price or time that is not advantageous in order to meet redemptions or other cash needs. Some securities may be subject to restrictions on resale. There can be no assurance that there will be a liquid market for instruments held by the Fund at any time. The Fund may not receive the proceeds from the sale of certain investments for an extended period.

Small and Mid-Cap Company RiskMarket risk and liquidity risk are particularly pronounced for securities of small and medium-sized companies, which may trade less frequently and in smaller volumes than more widely-held securities, and may fluctuate in price more than other securities. Their shares can be less liquid than those of larger companies, especially during market declines. Small and medium-sized companies may have limited product lines, markets, or financial resources and may be dependent on a limited management group; they may have been recently organized and have little or no track record of success.

The following risks under the heading Principal Risks (beginning on page 52 of the Prospectus) will be removed: Correlation Risk, Index Options Risk, Quantitative Models Risk, and REIT Risk.

The following information will replace the information for the Fund found under the heading Subadviser(s)in the section titled Management(on page 54 of the Prospectus):

Subadviser(s):J.P. Morgan Investment Management Inc. ("J.P. Morgan")

The following information will replace the information for the Fund found under the heading Portfolio Manager(s) in the section titled Management (on page 54 of the Prospectus):

Portfolio Manager(s):

Tim Snyder, CFA, CMT is an Executive Director and a portfolio manager at J.P. Morgan. He has managed the Fund since April 2026.

Raffaele Zingone, CFA is a Managing Director and a portfolio manager at J.P. Morgan. He has managed the Fund since April 2026.

The following information will replace similar information for the Fund found under the headings Annual Fund Operating Expenses and Examplein the section titled Fees and Expenses of the Fund(on page 51 of the Prospectus):

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund's operating expenses are exactly as described in the preceding table. If separate account or variable life insurance or variable annuity contract expenses were included, overall expenses would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

The following risks in the section titled Additional Information Regarding Principal Risks beginning on page 95 of the Prospectus will be removed: Correlation Risk and Index Options Risk.

The Bloomberg U.S. Aggregate Bond Index will also be removed as a secondary index for the Fund.

The following information will replace the information for Gateway found under the heading Subadvisers and Portfolio Managersin the section titled Management of the Fundson pages 121-122 of the Prospectus:

J.P. Morgan Investment Management Inc. ("J.P. Morgan"), located at 270 Park Avenue, New York, New York 10017, manages the investments of the MML VIP JP Morgan U.S. Research Enhanced Equity Fund. J.P. Morgan is a wholly-owned subsidiary of JP Morgan Asset Management Holdings Inc., which is a wholly-owned subsidiary of JP Morgan Chase & Co., a bank holding company. As of December 31, 2025, J.P. Morgan and its affiliates had approximately $4.1 trillion in assets under management.

J.P. Morgan replaced Gateway Investment Advisers, LLC as subadviser of the Fund on April 24, 2026.

Tim Snyder, CFA, CMT

is a portfolio manager of the MML VIP JP Morgan U.S. Research Enhanced Equity Fund. Mr. Snyder, Executive Director, joined J.P. Morgan in 2003 and is a portfolio manager on the U.S. Core Equity Team. His responsibilities include managing Research Enhanced Index (REI) strategies with a particular focus on tax aware U.S. equity mandates. Mr. Snyder joined the U.S. Core Equity portfolio management team in 2004 as an analyst and worked on the daily analysis, implementation, and maintenance of the REI and Analyst Fund portfolios. 

Raffaele Zingone, CFA

is a portfolio manager of the MML VIP JP Morgan U.S. Research Enhanced Equity Fund. Mr. Zingone, Managing Director, joined J.P. Morgan in 1991 and is a senior portfolio manager on the U.S. Core Equity Team. He is responsible for J.P. Morgan's Research Enhanced Index strategies and serves as co-portfolio manager on its Hedged Equity and Equity Premium Income strategies. Prior to this role, he was a research analyst following the aerospace, environmental, and diversified manufacturing sectors. Upon joining J.P. Morgan, Mr. Zingone was a quantitative equity analyst and later served as a U.S. Equity portfolio manager in London and New York.

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