Form 497K MASSMUTUAL SELECT FUNDS

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 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

The Fund seeks the highest total return over time consistent with an emphasis on both capital growth and income.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

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)

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. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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.

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

The Fund is a “fund of funds” and pursues its objective by investing in a diversified portfolio of other stock and bond series of both the MassMutual Select Funds and T. Rowe Price Funds that represent various asset classes and sectors (“Underlying Funds”). The Fund’s allocation between stock and bond funds will change over time in relation to its target retirement date. The Fund is subadvised by T. Rowe Price Associates, Inc. (“T. Rowe Price”). The Underlying Funds in which the Fund invests are predominantly either advised or subadvised by T. Rowe Price.

The Fund is managed based on the specific retirement year (target date 2010) included in its name and assumes a retirement age of 65. The target date refers to the approximate year an investor in the Fund would have retired and likely stopped making new investments in the Fund. The Fund is primarily designed for an investor who retired at or about the target date and who plans to withdraw the value of the account in the Fund gradually after retirement. However, if an investor retired earlier or later than age 65, the Fund may not be an appropriate investment even if the investor retired on or near the Fund’s target date.

Over time, the allocation to asset classes and funds will change according to a predetermined “glide path” shown in the following chart. The glide path represents the shifting of asset classes over time and shows how the Fund’s asset mix becomes more conservative–both prior to and after retirement–as time elapses. This reflects the need for reduced market risks as retirement approaches and the need for lower portfolio volatility after retiring. Although the glide path is meant to dampen the Fund’s potential volatility as retirement approaches, the Fund is not designed for a lump sum redemption at the retirement date. The Fund pursues an asset allocation strategy that promotes asset accumulation prior to retirement, but it is intended to also serve as a post-retirement investment vehicle with allocations designed to support an income stream made up of regular withdrawals throughout retirement along with some portfolio growth that exceeds inflation. After the target date, the Fund is designed to balance longevity and inflation risks along with the need for

some income, although it does not guarantee a particular level of income.

At the target date, the Fund’s allocation to stocks would have been approximately 55% of its assets. The Fund’s exposure to stocks will continue to decline until approximately 30 years after its target date, when its allocation to stocks will remain fixed at approximately 20% of its assets and the remainder will be invested in bonds. There are no maturity restrictions within the Fund’s overall allocation to bonds, although the bond funds in which the Fund invests may impose specific limits on maturity or credit quality. The allocations shown in the glide path are referred to as “neutral” allocations because they do not reflect any tactical decisions made by T. Rowe Price to overweight or underweight a particular asset class or sector based on its market outlook. The target allocations assigned to the broad asset classes (Stocks and Bonds), which reflect these tactical decisions resulting from market outlook, are not expected to vary from the neutral allocations set forth in the glide path by more than plus (+) or minus (-) five percentage (5%) points.

The following table details the way the portfolio is generally expected to be allocated between the asset classes. The table also shows the expected allocations to the Underlying Funds that will be used within those asset classes. The information in the table represents the neutral allocations for the Fund as of February 16, 2018. The target allocations and actual allocations may differ. The Fund’s shareholder reports set forth its actual allocations between stock funds and bond funds and to the individual Underlying Funds. T. Rowe Price may modify the target asset allocation strategy or the selection of Underlying Funds from time to time, and may invest in other Underlying Funds, including any Underlying Funds that may be created in the future. At any given time, the Fund’s asset allocation may be affected by a variety of factors (such as, for example, whether an Underlying Fund is accepting additional

investments). A description of the Underlying Funds is included in Appendix D of the Statement of Additional Information (“SAI”).

Through its investments in Underlying Funds, the Fund may be exposed to a wide range of securities and other instruments with differing characteristics (such as credit quality, duration, geography, industry, and market capitalization), including, but not limited to, equity securities of small-, mid-, or large-capitalization U.S. or non-U.S. issuers (including issuers that may only recently have become public companies), fixed income securities of U.S. or non-U.S. private or governmental issuers (including “junk” or “high yield” bonds, including securities in default), inflation-protected securities, bank loans, and short-term investments of any kind. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stock, real estate investment trusts (“REITs”), rights, and warrants.

An Underlying Fund may engage in foreign currency exchange transactions, including forward contracts, options on currency, futures contracts, and swap contracts, to take long or short positions in foreign currencies in order to enhance its investment return or to attempt to protect against adverse changes in currency exchange rates. An Underlying Fund may be permitted to use a wide variety of additional exchange-traded and over-the-counter derivatives, including options, futures contracts, swap contracts (including interest rate swaps, total return swaps, and credit default swaps), and hybrid instruments. An Underlying Fund may typically use these derivatives for hedging purposes, as a substitute for direct

investments, to earn additional income, to gain exposure to securities or markets in which it might not be able to invest directly, or to adjust various portfolio characteristics, including the duration (interest rate volatility) of the Fund’s portfolio of debt securities. Use of derivatives by an Underlying Fund may create investment leverage.

An Underlying Fund may enter into repurchase agreement transactions. An Underlying Fund may invest in mortgage-backed or other asset-backed securities. Some investments by an Underlying Fund may be restricted as to resale or otherwise considered to be illiquid. The Fund will bear a pro rata share of the Underlying Funds’ expenses. The Fund also bears all of the risks associated with the investment strategies used by the Underlying Funds.

Principal Risks

The following are the Principal Risks of the Fund. An investment in this Fund is not guaranteed. The value of your investment in the Fund could go down as well as up. You can lose money by investing in the Fund, including losses near, at, or after the target date. There is no guarantee that the Fund will provide adequate income at and through your retirement. Although the descriptions below refer to the risks relating to investment activities of the Fund, many of the risks arise due to the investment activities of the Underlying Funds.

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 other 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.

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 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.

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.

Commodities-Related Investments Risk Commodity prices (including precious metals) can be extremely volatile and exposure to commodities can cause the net asset value of the Fund’s shares to decline or fluctuate in a rapid and unpredictable manner. The values of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, real or perceived inflationary trends, commodity index volatility, changes in interest rates or currency exchange rates, population growth and changing demographics, international economic, political, and regulatory developments, or factors affecting a particular region, industry, or commodity. A liquid secondary market may not exist for certain commodity investments, which may make it difficult for the Fund to sell them at a desirable price or at the price at which it is carrying them.

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.

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.

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 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.

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, investor confidence, or announcements of economic, political, or financial information. While potentially offering greater opportunities for capital growth than larger, more established companies, the stocks of smaller companies may be particularly volatile, especially during periods of economic uncertainty. These

companies may face less certain growth prospects, or depend heavily on a limited line of products and services or the efforts of a small number of key management personnel.

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, and regulatory 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, terrorist attacks, war, 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), and credit risk. These risks may be heightened due to the current historically low interest rate environment.

Foreign Investment Risk; Emerging Markets Risk; Currency Risk Investments in securities of non-U.S. issuers (including depositary receipts) entail risks not typically associated with investing in securities of U.S. issuers. Similar risks may apply to securities traded on a U.S. securities exchange that are issued by companies with significant exposure to non-U.S. countries. In certain countries, legal remedies available to investors may be more limited than those available with regard to U.S. investments. 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 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. Foreign investments may be subject to the risks of seizure by a foreign government, imposition of restrictions on the exchange or export of foreign currency, other economic sanctions, and tax increases. 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, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody and operational risks, and greater volatility in currency exchange rates. Non-U.S. transaction costs, such as brokerage commissions and custody costs may be higher than in the United States. In addition, there may be a possibility of nationalization or expropriation of assets, imposition of currency exchange controls, confiscatory taxation, political or financial instability, and diplomatic developments that could adversely affect the values of the Fund’s investments in certain non-U.S. countries.

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.

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.

Large Company Risk Large-capitalization stocks as a group could fall out of favor with the market, causing the Fund to underperform investments that focus on small- or medium-capitalization stocks. Larger, more established companies may be slow to respond to challenges and may grow more slowly than smaller companies.

Leveraging Risk Instruments and transactions, including derivatives, 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 positions 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.

Management Risk The Fund relies on the manager’s investment analysis and its selection of investments to achieve its investment objective. There can be no assurance that the Fund will achieve the intended results and the Fund may incur significant losses.

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 markets can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical 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.

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. Investments that receive only the interest portion or the principal portion of payments on the underlying assets may be highly volatile. The market for mortgage- and asset-backed securities has recently experienced high volatility and a lack of liquidity. As a result, the value of many of these securities has significantly declined.

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.

Real Estate Risk; REIT Risk Real estate-related investments may decline in value as a result of factors affecting the real estate industry, such as the supply of real property in certain markets, changes in zoning laws, environmental regulations and other governmental action, delays in completion of construction, changes in real estate values, changes in property taxes, levels of occupancy, losses due to natural disasters, and local and regional market conditions. 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.

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

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, in which it invests, including the risk that the underlying funds will not perform as expected. The Fund indirectly pays a portion of the expenses incurred by the underlying funds.

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.

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.

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.

Performance Information

The Fund had not begun operations prior to the date of this prospectus, and therefore has no performance history. Because the Fund is new, there is no table which shows how the Fund’s returns have deviated from the broad market. Performance history will be available for the Fund after it has been in operation for one calendar year.

MANAGEMENT

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

Subadviser: T. Rowe Price Associates, Inc. (“T. Rowe Price”)

Portfolio Managers:

Jerome Clark, CFA is a Vice President and Portfolio Manager at T. Rowe Price. He has managed the Fund since its inception (February 2018).

Wyatt Lee, CFA is a Vice President and Portfolio Manager at T. Rowe Price. He has managed the Fund since its inception (February 2018).

PURCHASE AND SALE OF FUND SHARES

Shares of the Fund are generally available to retirement plans, 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).

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.