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Summary Prospectus February 1, 2025

MassMutual Funds

MassMutual Small Cap Opportunities Fund

Ticker: Class I–MSOOX, Class R5–MSCDX, Service Class–MSVYX, Administrative Class–MSCLX,
Class R4–MOORX, Class A–DLBMX, Class R3–MCCRX, Class Y–MMOGX

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 fundinfo@massmutual.com.

INVESTMENT OBJECTIVE

This Fund seeks 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 96 of the Fund’s Prospectus or from your financial professional.

Shareholder Fees (fees paid directly from your investment)

Class I

Class R5

Service
Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

Maximum Sales Charge (Load) Imposed on Purchases (as a % of offering price)

None

5.50%

None

Maximum Deferred Sales Charge (Load) (as a % of the lower of the original offering price or redemption proceeds)

None

1.00%(1)

None

(1)

Applies only to certain redemptions of shares bought with no front-end sales charge. Class A shares purchased without a front-end sales charge in accounts aggregating $1 million or more may be subject to a 1.00% contingent deferred sales charge if the shares are tendered and accepted for repurchase within 18 months of purchase. The 18-month period begins on the day on which the purchase is made.

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

	Class I	Class R5	Service Class	Administrative Class	Class R4	Class A	Class R3	Class Y
Management Fees	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%
Distribution and Service (Rule 12b-1) Fees	None	None	None	None	0.25%	0.25%	0.50%	None
Other Expenses	0.09%	0.19%	0.29%	0.39%	0.29%	0.34%	0.29%	0.19%
Total Annual Fund Operating Expenses	0.66%	0.76%	0.86%	0.96%	1.11%	1.16%	1.36%	0.76%
Expense Reimbursement	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)
Total Annual Fund Operating Expenses after Expense Reimbursement(1)	0.65%	0.75%	0.85%	0.95%	1.10%	1.15%	1.35%	0.75%

(1)

The expenses in the above table reflect a written agreement by MML Advisers 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 January 31, 2026, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed 0.65%, 0.75%, 0.85%, 0.95%, 1.10%, 1.15%, 1.35%, and 0.75% for Classes I, R5, Service, Administrative, R4, A, R3, and Y, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

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 at the end of each period:

	1 Year			3 Years			5 Years			10 Years
Class I		$	66		$	210		$	367		$	822
Class R5		$	77		$	242		$	421		$	941
Service Class		$	87		$	273		$	476		$	1,060
Administrative Class		$	97		$	305		$	530		$	1,177
Class R4		$	112		$	352		$	611		$	1,351
Class A		$	661		$	897		$	1,152		$	1,881
Class R3		$	137		$	430		$	744		$	1,634
Class Y		$	77		$	242		$	421		$	941

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 40% of the average value of its portfolio.

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

The Fund invests primarily in common stocks of small-capitalization U.S. companies that the Fund’s subadviser, Invesco Advisers, Inc. (“Invesco Advisers”), believes have favorable business trends or prospects based on fundamental analysis. Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in securities of small-cap companies. Invesco Advisers currently considers “small-cap” companies to be those whose market capitalizations at the time of purchase are within the market capitalization range of companies included in the Russell 2000® Index (as of December 31, 2024, between $6.12 million and $14.72 billion). The Fund typically invests most of its assets in equity securities of U.S. companies, but may invest in foreign securities, including emerging market securities; however, it does not currently intend to invest substantially in foreign securities. The Fund generally will not invest more than 15% of its total assets in foreign securities. The Fund may invest in other types of securities such as real estate investment trusts (“REITs”) or other securities that are consistent with its investment objective. The Fund may at

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times have significant exposure to one or more industries or sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

Invesco Advisers uses fundamental research to select securities for the Fund’s portfolio. While the process may change over time or vary in particular cases, in general the selection process currently uses a fundamental approach in analyzing issuers on factors such as a company’s financial performance, competitive strength and prospects, industry position, and business model and management strength. Industry outlook, market trends, and general economic conditions may also be considered.

Invesco Advisers aims to maintain a broad diversification across all major economic sectors. In constructing the portfolio, Invesco Advisers seeks to limit exposure to so-called “top-down” or “macro” risks, such as overall stock market movements, economic cycles, and interest rate or currency fluctuations. Instead, Invesco Advisers seeks to add value by selecting individual securities that it believes have superior company-specific fundamental attributes or relative valuations that they expect to outperform their industry and sector peers. This is commonly referred to as a “bottom-up” approach to portfolio construction.

Invesco Advisers considers stock rankings, benchmark weightings, and capitalization outlooks in determining security weightings for individual issuers. Invesco Advisers might sell a security if, for example, in its judgment, a stock’s price is approaching its target, a company’s competitive position deteriorates, a company’s management is performing poorly, or more attractive alternative investment ideas have been identified.

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. 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.

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.

Small and Mid-Cap Company Risk Market 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.

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, 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

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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.

Growth Company Risk The prices of growth securities are often highly sensitive to market fluctuations because of their heavy dependence on future earnings or cash flow expectations, and can be more volatile than the market in general.

Value Company Risk The value investment approach entails the risk that the market will not recognize a security’s intrinsic value for a long time, or that a stock the investment adviser or subadviser judges to be undervalued may actually be appropriately priced.

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.

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,

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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.

REIT Risk Investments in REITs may be subject to risks similar to those associated with direct investment in real estate, as well as additional risks associated with equity investments. As a shareholder in a REIT, the Fund, and indirectly the Fund’s shareholders, would bear its ratable share of the REIT’s expenses and would at the same time continue to pay its own fees and expenses.

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.

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.

Performance Information

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year for Class A shares. The returns in the bar chart do not reflect the deduction of any applicable Class A sales charge. If these charges were reflected, returns would be lower than those shown. The table shows how the Fund’s 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 more closely reflects the market segments in which the Fund invests (Russell 2000 Index). Performance for Class Y shares of the Fund for periods prior to its inception date (02/01/23) is based on the performance of Class R5 shares. Performance for Class A 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 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 A Shares

Highest Quarter:

2Q ’20,

28.30%

Lowest Quarter:

1Q ’20,

–30.90%

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 A only. After-tax returns for other classes will vary.

Average Annual Total Returns

(for the periods ended December 31, 2024)

		One Year			Five Years			Ten Years
Class A	Return Before Taxes		6.21	%		8.79	%		7.91	%
	Return After Taxes on Distributions		4.16	%		7.14	%		6.10	%
	Return After Taxes on Distributions and sales of Fund Shares		5.29	%		6.74	%		5.90	%
Class I	Return Before Taxes		12.96	%		10.62	%		9.12	%
Class R5	Return Before Taxes		12.84	%		10.49	%		9.00	%
Service Class	Return Before Taxes		12.76	%		10.40	%		8.90	%
Administrative Class	Return Before Taxes		12.65	%		10.29	%		8.79	%
Class R4	Return Before Taxes		12.46	%		10.12	%		8.63	%
Class R3	Return Before Taxes		12.17	%		9.85	%		8.36	%
Class Y	Return Before Taxes		12.88	%		10.51	%		9.01	%
Russell 3000® Index (reflects no deduction for fees, expenses, or taxes)(1)			23.81	%		13.86	%		12.55	%

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								One Year								Five Years								Ten Years
Russell 2000 Index (reflects no deduction for fees, expenses, or taxes)										11.54	%							7.40	%							7.82	%

(1)

Effective July 24, 2024, the Russell 3000 Index replaced the Russell 2000 Index as a broad measure of market performance in accordance with new regulatory disclosure requirements. The Fund continues to use the Russell 2000 Index as a supplemental benchmark that MML Advisers believes more closely reflects the market segments in which the Fund invests.

MANAGEMENT

Investment Adviser: MML Investment Advisers, LLC (“MML Advisers”)

Subadviser(s): Invesco Advisers, Inc. (“Invesco Advisers”)

Portfolio Manager(s):

Joy Budzinski is a Portfolio Manager at Invesco Advisers. She has managed the Fund since April 2013.

Magnus Krantz is a Portfolio Manager at Invesco Advisers. He has managed the Fund since April 2013.

Raman Vardharaj, CFA is a Portfolio Manager at Invesco Advisers. He has managed the Fund since May 2009.

Adam Weiner is a Co-Lead Portfolio Manager at Invesco Advisers. He has managed the Fund since April 2013.

Matthew P. Ziehl, CFA is a Co-Lead Portfolio Manager at Invesco Advisers. He has managed the Fund since May 2009.

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

Purchase Minimums*
	Class A	Class Y
Initial Investment	$1,000	$100,000
Subsequent Investment	$250	$250

The Fund reserves the right to change or waive the investment minimums. Class I, Class R5, Service Class, Administrative Class, Class R4, and Class R3 shares do not have investment minimums and there are no initial or subsequent investment minimums for retirement plans.

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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