Summary Prospectus by Investment Company (Form 497K)

MassMutual Funds

MML Barings Unconstrained Income Fund
(formerly known as MassMutual Global Credit Income Opportunities Fund)
(Class M1 and Class M2 shares not currently available)

Ticker: Class I-BXITX, Class Y-BXIYX, Class A-BXIAX, Class C-BXICX, Class M1-BXIEX,
Class M2-BXIDX

Before you invest, you may want to review the Fund's prospectus, which contains more information about the Fund and its risks. You can find the Fund's prospectus and other information about the Fund online at https://www.massmutual.com/funds. You can also get this information at no cost by calling 1-888-309-3539 or by sending an email request to [email protected].

INVESTMENT OBJECTIVE

This Fund seeks an absolute return, primarily through current income and secondarily through capital appreciation.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay brokerage commissions and other fees to financial intermediaries which are not reflected in the tables and examples below. For Class A shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in MassMutual Funds. More information about these and other discounts is available in the section titled Sales Charges by Class beginning on page 66 of the Fund's Prospectus or from your financial professional.

Shareholder Fees (fees paid directly from your investment)

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

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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. For Class A shares, the example includes the front-end sales charge. 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. Although your actual costs  may be higher or lower, based on these assumptions your costs would be:

You would pay the following expenses if you did not redeem your shares:

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not

reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 87% of the average value of its portfolio.

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

The Fund is managed using an absolute return investment objective, which means that it is not managed relative to the performance of a specific bond index, but rather seeks to generate positive returns over the course of a full market cycle while managing volatility through security selection and possibly hedging to reduce overall exposure to credit and interest rate risk. The Fund seeks absolute total return through a combination of current income and capital appreciation.

Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in debt instruments (consisting of loans, bonds, and notes). The Fund may invest in a wide range of debt instruments of issuers based in  U.S. and non-U.S. markets, including emerging markets, as well as over-the-counter and exchange-traded derivatives. Investments may be issued or guaranteed by governments and their agencies, corporations, financial institutions, and supranational organizations that the Fund believes have the potential to provide a high total return over time. A significant portion of the Fund's investments in debt instruments are denominated in a currency other than the U.S. dollar. Although the Fund's investment in non-U.S. dollar-denominated assets may be on a currency hedged or unhedged basis,

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under normal market conditions, the Fund seeks to hedge substantially all of its exposure to non-U.S. currencies. The Fund may at times have significant exposure to one or more industries or sectors.

Under normal market conditions, the Fund allocates its assets among various regions and countries (but in no less than three different countries) and invests at least 40% of its net assets in securities of  non-U.S. issuers (or, if less, at least the percentage of net assets that is 5 percentage points less than the percentage of the ICE BofA Non-Financial Developed Markets High Yield Constrained Index, represented by non-U.S. issuers, as determined by the provider of the index). Although the ICE BofA Non-Financial Developed Markets High Yield Constrained Index is representative of the Fund's investable universe, the Fund does not seek to be correlated with that index.

The Fund seeks to take advantage of inefficiencies between geographies, primarily the North American and Western European high yield bond and loan markets and within capital structures between bonds and loans. For example, the Fund seeks to take advantage of differences in pricing between bonds or loans of an issuer denominated in  U.S. dollars and substantially similar bonds or loans of the same issuer denominated in Euros, potentially allowing the Fund to achieve a higher relative return for the same credit risk exposure.

The Fund invests primarily in high yield debt instruments (consisting of bonds, loans, and notes) of North American and Western European corporate issuers that are of below investment grade quality. The Fund invests in instruments that are, at the time of purchase, rated below investment grade ("junk" or "high yield") by at least one credit rating agency (below Baa3 by Moody's Investors Service, Inc. or below BBB- by either S&P Global Ratings, a subsidiary of S&P Global, or Fitch Ratings, Inc.) or, if unrated, determined to be of comparable quality by the Fund's subadviser, Barings LLC ("Barings"), or sub-subadviser, Baring International Investment Limited ("BIIL").

The Fund invests primarily in high yield bonds, loans, and notes, but also makes use of a wide range of debt instruments. The Fund may invest in both fixed and floating rate instruments; listed and unlisted corporate debt obligations; convertible securities; structured products (consisting of  collateralized bond and loan obligations); bank obligations; U.S. and non-U.S. government securities; preferred securities and trust preferred securities; asset-backed securities; unsecured loans; delayed funding loans and revolving credit facilities;

when-issued securities, delayed delivery purchases, and forward commitments; zero-coupon bonds, step-up bonds, and payment-in-kind securities; commercial paper; repurchase agreements; and other investment companies. The Fund's investments may include investments in the lowest rating category of the applicable rating agency. The Fund may invest in distressed bonds and loans that are in default at the time of purchase in an effort to protect the Fund's existing investment in securities of the same issuers. The Fund also may invest in equity securities (consisting of common and preferred stocks, warrants and rights, and limited partnership interests), but will invest in such equity investments only for the preservation of capital. The Fund may hold a portion of its assets in cash or cash equivalents.

The Fund may invest in fixed income securities or debt instruments issued by emerging market entities or sovereign nations. Emerging market countries are defined to include any country that did not become a member of the Organization for Economic Cooperation and Development (O.E.C.D.) prior to 1975 and Turkey.

The Fund may also use derivatives to a significant extent for risk management and hedging purposes, or for speculative purposes - as substitutes for investments in securities in which the Fund can invest - in order to achieve the Fund's absolute return objective and manage volatility. The Fund may use over-the-counter and exchange-traded derivatives for a variety of purposes, consisting of: as a hedge against adverse changes in the market price of securities, interest rates, or currency exchange rates; as a substitute for purchasing or selling securities; and to increase the Fund's yield or return as a non-hedging strategy that may be considered speculative. The Fund may establish, through derivatives, net short positions for individual sectors, markets, currencies, or securities, or as a means of adjusting the Fund's portfolio duration, credit quality, and maturity. The Fund may invest in over-the-counter and  exchange-traded derivative instruments provided that, at the time the Fund enters into a derivative transaction, the Fund segregates assets determined to be liquid by Barings or BIIL in accordance with procedures established by the Fund's Board of Trustees, in an amount at least equal to any payment or delivery obligation of the Fund in connection with such derivative transaction. The Fund's use of derivatives may consist primarily of total return swaps, options, index swaps or swaps on components of an index, interest rate swaps, credit default swaps, and foreign currency forward contracts and futures.

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The Fund may invest in investments of any duration or maturity.

The Fund may borrow up to one-third of its assets (including the amount borrowed) to fund redemptions, post collateral for hedges, or to purchase loans, bonds, or structured products prior to settlement of pending sale transactions.

Securities may be sold when  Barings or BIIL believes they no longer represent relatively attractive investment opportunities.

Principal Risks

The following are the Principal Risks of the Fund. The value of your investment in the Fund could go down as well as up. You can lose money by investing in the Fund. References in this section to the Fund's subadviser may include any sub-subadvisers as applicable. Certain risks relating to instruments and strategies used in the management of the Fund are placed first. The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Fixed Income Securities Risk The values of fixed income securities typically will decline during periods of rising interest rates, and can also decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral assets, or changes in market, economic, industry, political, regulatory, public health, and other conditions affecting a particular type of security or issuer or fixed income securities generally. Certain events, such as market or economic developments, regulatory or government actions, natural disasters, pandemics, terrorist attacks, war, rapid technological developments or widespread adoption of new technologies (such as artificial intelligence), and other geopolitical events can have a dramatic adverse effect on the debt market and the overall liquidity of the market for fixed income securities. During those periods, the Fund may experience high levels of shareholder redemptions, and may have to sell securities at times when the Fund would otherwise not do so, and potentially at unfavorable prices. Certain securities may be difficult to value during such periods. Fixed income securities are subject to interest rate risk (the risk that the value of a fixed income security will fall when interest rates rise), extension risk (the risk that the average life of a security will be extended through a slowing of principal payments), prepayment risk (the risk that a security will be

prepaid and the Fund will be required to reinvest at a less favorable rate), duration risk (the risk that longer-term securities may be more sensitive to interest rate changes), inflation risk (the risk that as inflation increases, the present value of the Fund's fixed income investment typically will decline), and credit risk. Fiscal, economic, monetary, or other governmental policies or measures have in the past, and may in the future, cause or exacerbate certain risks, including interest rate risks.

Bank Loans Risk Many of the risks associated with bank loans are similar to the risks of investing in below investment grade debt securities. Changes in the financial condition of the borrower or economic conditions or other circumstances may reduce the capacity of the borrower to make principal and interest payments on such instruments and may lead to defaults. Senior secured bank loans are typically supported by collateral; however the value of the collateral may be insufficient to cover the amount owed to the Fund, or the Fund may be prevented or delayed from realizing on the collateral. Some loans may be unsecured; unsecured loans generally present a greater risk of loss to the Fund if the issuer defaults. If the Fund relies on a third party to administer a loan, the Fund is subject to the risk that the third party will fail to perform its obligations. In addition, if the Fund holds only a participation interest in a loan made by a third party, the Fund's receipt of payments on the loan will depend on the third party's willingness and ability to make those payments to the Fund. The settlement time for certain loans is longer than the settlement time for many other types of investments, and the Fund may not receive the payment for a loan sold by it until well after the sale; that cash would be unavailable for payment of redemption proceeds or for reinvestment. Interests in some bank loans may not be readily marketable and may be subject to restrictions on resale. In some cases, negotiations involved in disposing of indebtedness may require weeks to complete. Consequently, some indebtedness may be difficult or impossible to dispose of readily at what the Fund believes to be a fair price. Some loans may not be considered "securities" for certain purposes under the federal securities laws, and purchasers, such as the Fund, therefore may not be entitled to rely on the anti-fraud protections of the federal securities laws.

Below Investment Grade Debt Securities Risk Below investment grade debt securities, commonly known as "junk" or "high yield" bonds, have speculative characteristics and involve greater volatility of price

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and yield, greater risk of loss of principal and interest, and generally reflect a greater possibility of an adverse change in financial condition that could affect an issuer's ability to honor its obligations.

Credit Risk Credit risk is the risk that an issuer, guarantor, or liquidity provider of a fixed income security held by the Fund may be unable or unwilling, or may be perceived (whether by market participants, ratings agencies, pricing services or otherwise) as unable or unwilling, to make timely principal and/or interest payments, or to otherwise honor its obligations. The Fund may also be exposed to the credit risk of its counterparty to repurchase agreements, reverse repurchase agreements, swap transactions, and other derivatives transactions, and to the counterparty's ability or willingness to perform in accordance with the terms of the transaction. The value of such transactions to the Fund will depend on the willingness and ability of the counterparty to perform its obligations, including among other things the obligation to return collateral or margin to the Fund. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Fund may experience significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Fund may obtain only a limited recovery or may obtain no recovery in such circumstances.

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 Risk Investments 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

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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.

Mortgage- and Asset-Backed Securities Risk Investments in mortgage- and asset-backed securities subject the Fund to credit risk, interest rate risk, extension risk, and prepayment risk, among other risks. Mortgage-backed and asset-backed securities not issued by a government agency generally involve greater credit risk than securities issued by government agencies. Payment of principal and interest generally depends on the cash flows generated by the underlying assets and the terms of the security. The types of mortgages (for example, residential or commercial mortgages) underlying securities held by the Fund may differ and be affected differently by market factors. The Fund's investments in mortgage-backed securities may make the Fund's net asset value more susceptible to economic, market, political, and other developments affecting the residential and commercial real estate markets and the servicing of mortgage loans secured by real estate properties. During periods of difficult economic conditions, delinquencies and losses on commercial mortgage-backed investments in particular generally increase, including as a result of the effects of those conditions on commercial real estate markets, the ability of commercial tenants to make loan

payments, and the ability of a property to attract and retain commercial tenants. Investments that receive only the interest portion or the principal portion of payments on the underlying assets may be highly volatile. Litigation with respect to the representations and warranties given in connection with the issuance of mortgage-backed securities can be an important consideration in investing in such securities, and the outcome of any such litigation could significantly impact the value of the Fund's mortgage-backed investments.

Structured Notes Risk Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market, or interest rate ("reference measure"). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of a structured note's value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities.

Cash Position Risk If the Fund holds a significant portion of its assets in cash or cash equivalents, its investment returns may be adversely affected and the Fund may not achieve its investment objective.

Collateralized Loan Obligations and Other Collateralized Obligations Risk. An investment in a collateralized loan obligation can be viewed as investing in (or through) another investment adviser and is subject to the layering of fees associated with such an investment. The risks of investing in a collateralized loan obligation generally can be summarized as a combination of economic risks of the underlying loans combined with the risks associated with the collateralized loan obligation structure governing the priority of payments, and include interest rate risk, credit risk, liquidity risk, prepayment risk, and the risk of default of the underlying asset, among others.

Convertible Securities Risk Convertible securities are subject to the risks of both debt instruments and equity securities. The price of a convertible security may change in response to changes in price of the underlying equity security, the credit quality of the issuer, and interest rates. In general, the values of convertible securities tend to decline as interest rates rise and to rise when interest rates fall. A convertible security generally has less potential for gain or loss than the underlying equity security.

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Covenant Lite Loans Risk Loans in which the Fund invests include covenant lite loans, which may carry more risk to the lender than traditional loans as they may contain fewer restrictive covenants on the borrower than traditionally included in loan documentation or may contain other borrower-friendly characteristics. The Fund may experience relatively greater difficulty or delays in enforcing its rights on its holdings of certain covenant lite loans and debt securities than its holdings of loans or securities with the usual covenants.

Defaulted and Distressed Securities Risk Because the issuer of such securities is in default and is likely to be in distressed financial condition, repayment of defaulted securities and obligations of distressed issuers (including insolvent issuers or issuers in payment or covenant default, in workout or restructuring, or in bankruptcy or insolvency proceedings) is uncertain. To the extent the Fund is invested in distressed securities, its ability to achieve current income for its shareholders may be diminished.

Equity Securities Risk Although stocks may have the potential to outperform other asset classes over the long term, their prices tend to fluctuate more dramatically over the shorter term. These movements may result from factors affecting individual companies, or from broader influences like changes in interest rates, market conditions, or investor confidence, or announcements of economic, political, or financial information.

Hedging Risk The Fund's attempts at hedging and taking long and short positions in currencies may not be successful and could cause the Fund to lose money or fail to get the benefit of a gain on a hedged position. If expected changes to securities prices, interest rates, currency values, and exchange rates, or the creditworthiness of an issuer are not accurately predicted, the Fund could be in a worse position than if it had not entered into such transactions.

Inflation Risk The value of assets or income from the Fund's investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Fund's assets can decline as can the value of the Fund's distributions. Inflation rates may change frequently and drastically as a result of various factors, including unexpected shifts in the domestic or global economy (or expectations that such policies will change), and the Fund's investments may not keep pace with inflation, which may result in losses to the Fund's investors.

Leveraging Risk Instruments and transactions, including derivatives transactions, that create leverage may cause the value of an investment in the Fund to be more volatile, could result in larger losses than if they were not used, and tend to compound the effects of other risks.

Liquidity Risk Certain 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.

Management and Operational Risk The Fund relies on the manager's investment analysis and its selection of investments to achieve its investment objective, and the Fund is subject to the risk that the manager's assessment of an investment is wrong. There can be no assurance that the Fund will achieve the intended results and the Fund may incur significant losses. The Fund also runs the risk that deficiencies in the investment adviser's, subadviser's, or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

Market Risk The value of the Fund's portfolio securities may decline, at times sharply and unpredictably, as a result of unfavorable market-induced changes affecting particular industries, sectors, or issuers. Stock and bond markets can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, public health, and other conditions, as well as investor perceptions of these conditions. The Fund is subject to risks affecting issuers, such as management performance, financial leverage, industry problems, and reduced demand for goods or services.

Preferred Stock Risk Like other equity securities, preferred stock is subject to the risk that its value may decrease based on actual or perceived changes in the business or financial condition of the issuer. In addition, changes in interest rates may adversely affect the value of a preferred stock that pays a fixed dividend. Preferred stocks are also subject to

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additional risks, such as potentially greater volatility and risks related to deferral, non-cumulative dividends, subordination, liquidity, limited voting rights, and special redemption rights.

Reinvestment Risk Income from the Fund's portfolio will decline if and when the Fund invests the proceeds from matured, traded, or called debt obligations at market interest rates that are below the portfolio's current earnings rate. A decline in income could affect the Fund's overall return.

Repurchase Agreement Risk These transactions must be fully collateralized, but involve credit risk to a Fund if the other party should default on its obligation and the Fund is delayed or prevented from recovering the collateral.

Restricted Securities Risk The Fund may hold securities that are restricted as to resale under the U.S. federal securities laws, such as securities in certain privately held companies. Such securities may be highly illiquid and their values may experience significant volatility. Restricted securities may be difficult to value.

Risk of Investment in Other Funds or Pools The Fund is indirectly exposed to all of the risks of the underlying funds, including exchange-traded funds ("ETFs"), in which it invests, including the risk that the underlying funds will not perform as expected. ETFs are subject to additional risks, including secondary market trading risks and the risk that an ETF's shares may trade above or below net asset value.  Shareholders bear both their proportionate share of the Fund's expenses and similar expenses of the underlying fund or ETF when the Fund invests in shares of another registered investment company or ETF. ETFs may trade at a price above (premium) or below (discount) their net asset value, especially during periods of significant market volatility or stress, causing investors to pay significantly more or less than the value of the ETF's underlying portfolio.

Sector Risk The Fund may allocate more of its assets to particular industries or to particular economic, market, or industry sectors than to others. This could increase the volatility of the Fund's portfolio, and the Fund's performance may be more susceptible to developments affecting issuers in those industries or sectors than if the Fund invested more broadly.

Sovereign Debt Obligations Risk Investments in debt securities issued by governments or by government agencies and instrumentalities involve the risk that the governmental entities responsible for repayment may be unable or unwilling to pay interest and repay

principal when due. Many sovereign debt obligations may be rated below investment grade ("junk" or "high yield" bonds). Any restructuring of a sovereign debt obligation held by the Fund will likely have a significant adverse effect on the value of the obligation. In the event of default of sovereign debt, the Fund may be unable to pursue legal action against the sovereign issuer or to realize on collateral securing the debt.

U.S. Government Securities Risk Obligations of certain U.S. Government agencies and instrumentalities are not backed by the full faith and credit of the U.S. Government, and there can be no assurance that the U.S. Government would provide financial support to such agencies and instrumentalities.

Valuation Risk The Fund is subject to the risk of mispricing or improper valuation of its investments, in particular to the extent that its securities are fair valued.

When-Issued, Delayed Delivery, TBA, and Forward Commitment Transaction Risk These transactions may create leverage and involve a risk of loss if the value of the securities declines prior to settlement.

Performance Information

The following bar chart and table provide some indication of the risks of investing in the Fund. The Fund is the successor to the Barings Global Credit Income Opportunities Fund (the "Predecessor Fund"), a mutual fund with substantially similar investment objectives, policies, and restrictions, as a result of the reorganization of the Predecessor Fund into the Fund on December 13, 2021. The performance provided in the bar chart and table is that of the Predecessor Fund prior to December 13, 2021, and is that of the Fund after December 13, 2021. The bar chart shows changes in the Fund's (or Predecessor Fund's, as applicable) performance from year to year for Class I shares. The table shows how the Fund's (or Predecessor Fund's, as applicable) average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance and an additional index that MML Advisers believes is a better comparison for the Fund's investment strategy (FTSE 3 Month US T Bill Index). Performance for Class M1 and Class M2 shares of the Fund (which have not yet begun operations, and therefore have no performance history) is based on the performance of Class I shares. Performance for Class A and Class C shares of the Fund reflects any applicable sales charge. Past performance (before and after taxes) is not necessarily an indication of how the Fund will

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perform in the future. More up-to-date performance information is available at https://www.massmutual.com/product-performance/mutual-funds  or by calling 1-888-309-3539.

Annual Performance

Class I Shares

After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class I  only. After-tax returns for other classes will vary.

Average Annual Total Returns
(for the periods ended December 31, 2025)

MANAGEMENT

Investment Adviser: MML Investment Advisers, LLC ("MML Advisers")

Subadviser(s): Barings LLC ("Barings")

Sub-subadviser(s): Baring International Investment Limited ("BIIL")

Portfolio Manager(s):

Chris Ellis is a Managing Director and a portfolio manager for Barings' European High Yield Investment Group. He has managed the Fund since September 2023.

Sean  Feeley, CFA is a Managing Director and portfolio manager for Barings' U.S. High Yield Investment Group. He has managed the Fund since September 2013.

Omotunde Lawal, CFA is a Managing Director, the Head of  EMEA Corporate Credit and Emerging Markets Corporate Debt, and the lead portfolio manager for the Emerging Markets Corporate Debt, Emerging Markets Short Duration, and EMEA Investment Grade strategies. She has managed the Fund since May 2021.

Brian Pacheco, CFA is a Managing Director and portfolio manager for Barings' Global High Yield Investment Group. He has managed the Fund since February 2023.

Scott Roth, CFA is a Managing Director and the Head of, and a portfolio manager for, Global High Yield at Barings. He has managed the Fund since September 2013.

Chris Sawyer is a Managing Director and the Head of, and a portfolio manager for, Barings' European High Yield Investment Group. He has managed the Fund since May 2021.

PURCHASE AND SALE OF FUND SHARES

Shares of the Fund are generally available through various financial intermediaries, such as retirement plan recordkeepers, broker-dealers, financial institutions, and insurance companies, and to other

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institutional investors and individual retirement accounts. Fund shares are redeemable on any business day by written request, telephone, or internet (available to certain customers).

TAX INFORMATION

The Fund intends to make distributions that may be taxed as ordinary income, qualified dividend income, or capital gains, unless you are an investor eligible for preferential tax treatment.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you purchase the Fund through a broker-dealer or other financial intermediary, the intermediary may receive a one-time or continuing payments from the Fund, MML Advisers or its affiliates, or others for the sale of Fund shares or continuing shareholder services provided by the intermediary. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary to recommend the Fund over another investment. You should contact your intermediary to obtain more information about the compensation it may receive in connection with your investment.

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