Fund Russell 1000® Growth Index

Sector Weightings: Defines what % of each sector this fund holdscompared to its benchmark listed here.

QTD YTD

Portfolio Attribution: Describes how fund manager sector and stockweighting decisions affected returns.

Sector Attribution Details: Sector Fund Weight Q T D Y T D

Communication Services 23.15 1.71 8.86

Consumer Discretionary 11.12 -0.66 -1.07

Consumer Staples 0.81 0.09 0.45

Energy 0.00 -0.01 0.16

Financials 1.32 0.21 -0.68

Health Care 12.11 1.19 1.79

Industrials 7.37 0.98 3.20

Information Technology 40.93 1.54 4.82

Materials 1.29 0.05 0.45

Real Estate 0.00 0.25 1.09

Utilities 0.00 -0.00 0.00

Cash 1.90 -0.26 -0.51

Quarterly Portfolio Commentary:

Jason Marino, CFA, CAIA Investment DirectorInvestment Experience: 19 Years

HIGHLIGHTS • Despite returning more than 11% in the quarter, the Russell 1000®Growth Index was the worst performing domestic equity index in theperiod.• All but one sector, real estate, posted positive returns in the quarter.• Stock selection, positive in six of eight invested sectors, was the maincontributor to the Fund’s relative outperformance.• Sector allocation was slightly positive, due in part to an overweightallocation to communication services.

Fund Objective: This Fund seeks long-term capital appreciation.

These materials and the platform of investments made available by MassMutual are offered without regard to the individualized needs of any plan, itsparticipants, or beneficiaries. These materials are not intended as impartial investment advice or to give advice in a fiduciary capacity to any plan.

NOT FDIC INSURED MAY LOSE VALUE NO BANK GUARANTEE

Quarterly Review

I SHARE CLASS TICKER: MMAZX

As of 12/31/2020

MassMutual Select Growth Opportunities FundSands Capital Management, LLC | Jackson Square Partners, LLC

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Quarterly Portfolio Commentary:

The Russell 1000® Growth Index had its best calendar year return in 20 years, a fitting encore to 2019, which now stands as the third highest return in 20years. Despite that, the Russell 1000 Growth Index was the worst performing domestic equity index in the quarter. Investor appetite for risk drove small-cap equities to outperform their large-cap counterparts influenced by the positive developments on a COVID-19 vaccine. Five of 11 index sectorsoutperformed the Index’s aggregate return. The energy sector was the top performing sector, returning more than 28% as the price of oil moved higher.The sector represents less than 1/10th of a percent of weight within the index, severely limiting its impact. The worst performing sector, real estate, alsohad its impact limited by its relatively small weight in the Index at less than 2%. The information technology sector, the largest sector by weight, was thelargest contributor to Index returns. Strong price appreciation of the Index’s largest constituent, Apple, placed the company as the top contributor in thesector. The consumer discretionary sector was the second largest contributor to Index returns. The majority of contribution came from electric carmanufacturer Tesla Inc. The company’s shares posted strong price gains as the stock was included in the S&P 500® Index.

The Fund outperformed both the Russell 1000® Growth Index and the large-cap growth peer group for the quarter. The Index was particularly difficult tobeat for most of 2020, outperforming most active managers for the full-year. The fourth quarter did see a reversal of that trend, with the majority ofmanagers outperforming the Index. Strong stock selection was the primary driver of the Fund’s relative returns with sector allocation modestlycontributing as well. Overall, Fund management added value in eight of the benchmark’s 11 sectors.

Sector wise, the Fund’s overweight to communication services and an underweight to the real estate sectors had the largest positive impact. Sectorallocation is a function of each manager’s bottom-up process and an outcome of where they find companies fitting their investment process and criteria.

Positive stock selection within the majority of sectors was the main driver of relative outperformance. Selection within the information technologysector, the Fund’s largest sector by weight, was the strongest. Two of the Fund’s top five overall contributors – Twilio Inc and Square – reside in thesector. Twilio, a cloud-based communications software provider, realized share price gains of more than 36% in the quarter after posting better-than-expected revenue results. The share price of Square, a payment processor, gained more than 33% in the quarter as the company posted better-than-expected earnings and strong momentum in its Cash App Business.

Stock selection was also strong within the communication services sector, the Fund’s second largest sector by weight and home to the Fund’s largestabsolute contributor to returns, online dating company Match Group Inc. The company’s share price posted impressive gains in the quarter as it’s Tinderdating app subscriber growth topped expectations. Five of the Fund’s eight holdings in the sector returned more than 19% in the quarter, pointing towidespread strength of the sector in the Fund. The consumer discretionary sector was an area of weak stock selection. The driver of relativeunderperformance was an avoidance of Tesla, accounting for all the relative weakness within the sector and offsetting positive relative contribution fromboth Floor & Décor Holdings and Starbucks Corp.

The Fund’s largest underweight allocations are to the information technology and consumer discretionary sectors. The largest overweight allocationremains the communication services sector followed by the industrials sector.

TICKER: MMAZX Fund Inception: 4/28/2000Morningstar Category: Large Cap Growth

Average Annual Total Return

Q T D Y T D 1 Y 3 Y 5 Y 1 0 Y

MassMutual Select Growth Opps I 17.08% 58.05% 58.05% 28.20% 21.05% 17.98%

Russell 1000® Growth Index 11.39% 38.49% 38.49% 22.99% 21.00% 17.21%

Category Average Returns -- -- 35.86% 20.50% 18.30% 15.14%

Category Rank -- -- 8 8 17 11

# of Funds in Category -- -- 1289 1197 1070 789 Performance shown is for class I shares. Gross expenses = 0.76%, Net expense = 0.76%. Max Sales charge for I is 0.00%.Performance shown is past performance. Past performance does not guarantee future results . You can lose money, includingloss of pr incipal , by invest ing in this fund. Investors should careful ly consider investment objectives, r isks , charges andexpenses. This and other important information is contained in the fund prospectuses and summary prospectuses, which can beobtained from www.massmutualfunds.com and should be read careful ly before invest ing. A l ist of the Fund’s holdings can alsobe obtained from www.massmutualfunds.com. Current performance may be lower or higher than return data quoted herein. Formore current information, including month-end performance, please cal l 1-866-444-2601. You cannot invest directly in an index.Pre-Inception Returns - The inception date listed is that of the oldest share class of the Fund. Performance shown subsequent to the inception date

is the actual performance of the share class. Other share classes of the investment itself have existed longer, which accounts for any pre-inceptionperformance shown. The pre-inception performance of Class I for the periods prior to its inception date of (12/07/2011) is based on the performance of anolder share class, Class R5, using the expenses and fees of Class R5 (inception date 05/01/2000). If the expenses of the newer share class was used ratherthan the expenses of the old share class (due to lower expenses of the new share class), it would have resulted in better performance.The Fund’s Princ ipa l R isks include - Equity Securities Risk, Foreign Investment Risk, Emerging Markets Risk, Currency Risk, Growth Company Risk,Large Company Risk, Small and Mid-Cap Company Risk, Cash Position Risk, Convertible Securities Risk, Liquidity Risk, Management Risk, Market Risk,Preferred Stock Risk, Sector Risk, Valuation Risk.The Morningstar percenti le ranking is based on the fund’s total-return percenti le rank relat ive to al l funds that have the same

category for the same t ime period. The highest (or most favorable) percentile rank is 1%, and the lowest (or least favorable) percentile rank is 100%.Morningstar total return includes both income and capital gains or losses and is not adjusted for sales charges. ©2021 Morningstar, Inc. All Rights Reserved.The information contained herein: (1) is proprietary to Morningstar and/or its content providers; (2) may not be copied or distributed; and (3) is notwarranted to be accurate, complete or timely. Neither Morningstar nor its content providers are responsible for any damages or losses arising from any useof this information.

MassMutual Select Growth Opportunities Fund

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Quarter to Date:

Top 5 Contributors F u n dW e i g h t

AbsoluteReturn*

Portfol ioContr ibut ion

Match Group Inc 4.53 36.64 1.53

Uber Technologies Inc 4.36 39.80 1.46

Twilio Inc A 4.24 36.99 1.32

Sea Ltd ADR 4.37 29.22 1.20

Square Inc A 3.47 33.89 1.07

Top 5 Detractors F u n dW e i g h t

AbsoluteReturn*

Portfol ioContr ibut ion

DoorDash Inc OrdinaryShares - Class A 0.14 -23.25 -0.17

DexCom Inc 0.60 -10.31 -0.08

Wix.com Ltd 1.03 -1.92 -0.02

Grocery Outlet HoldingCorp 0.77 -0.18 -0.00

USTREAS T-Bill Auction Ave3 Mon 1.90 0.02 0.00

Year to Date:

Top 5 Contributors F u n dW e i g h t

AbsoluteReturn*

Portfol ioContr ibut ion

Sea Ltd ADR 2.77 394.90 5.53

Twilio Inc A 2.95 244.42 4.67

Amazon.com Inc 6.72 76.26 4.44

ServiceNow Inc 5.02 94.97 4.16

Square Inc A 1.97 206.32 3.40

Top 5 Detractors F u n dW e i g h t

AbsoluteReturn*

Portfol ioContr ibut ion

Constellation Brands Inc A 0.51 -25.58 -0.76

Hasbro Inc 0.30 -39.85 -0.59

Charles Schwab Corp 0.55 -29.53 -0.53

CME Group Inc Class A 0.93 -16.69 -0.35

Applied Materials Inc 0.33 -21.83 -0.32

RS9093b RS-49187-03

Portfolio Holdings:

Fund Weightings are shown as an average for the time period.*Absolute Return is the return that an asset achieves over a certain period of time. This measure looks at the appreciation or depreciation (expressed as apercentage) that a holding achieves over a given period of time.For a complete listing of fund holdings, visit massmutualfunds.com or please call 1-866-444-2601. The mention of individual stocks and other securities inthis document does not constitute investment advice.

©2021 Massachusetts Mutual Life Insurance Company (MassMutual®), Springfield, MA. All rights reserved. www.MassMutual.com Principal Underwriter:MML Distributors, LLC. (MMLD), 1295 State St., Springfield, MA 01111. Member FINRA and SIPC (www.FINRA.org and www.SIPC.org). Investment advisoryservices provided to the Funds by MML Investment Advisers, LLC (MML Investment Advisers). MMLD and MML Investment Advisers are subsidiaries ofMassachusetts Mutual Life Insurance Company (MassMutual), Springfield, MA 01111-0001.

MassMutual Select Growth Opportunities Fund

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