Merck & Co., Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant

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Filed by a Party other than the Registrant

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Merck & Co., Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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Notice of Annual Meeting of Shareholders

To Shareholders:

You are invited to the Annual Meeting of Shareholders of Merck & Co., Inc., Rahway, NJ, U.S.A. (the “Company”) on Tuesday, May 26, 2026, at 9:00 a.m. (Eastern Time) via Webcast atwww.virtualshareholdermeeting.com/MRK2026(the “2026 Annual Meeting”).

The purposes of the 2026 Annual Meeting are to:

1. Elect the 13 Director nominees named in this proxy statement;

2. Consider and act upon a proposal to approve, bynon-binding advisory vote, the compensation of our Named Executive Officers;

3. Consider and act upon a proposal to ratify the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public accounting firm for 2026;

4. Consider and act upon a shareholder proposal regarding a report on DEI risks in federal contracting, if properly presented at the meeting;

5. Consider and act upon a shareholder proposal regarding a report on healthcare coverage gaps, if properly presented at the meeting;

6. Consider and act upon a shareholder proposal regarding a report on political contributions, if properly presented at the meeting; and

7. Transact such other business as may properly come before the meeting.

By order of the Board of Directors,

Kelly E. W. Grez

Corporate Secretary

Vote Right Away—Advance voting methods and deadlines

We encourage all shareholders of record to read this proxy statement with care and vote right away using any of the following methods, even if they intend to attend the 2026 Annual Meeting. In all cases, have your proxy card or voting instruction form in hand and follow the instructions.

Only shareholders listed on the Company’s records at the close of business on March 27, 2026 are entitled to vote.

The Company began distributing its Notice of Internet Availability of Proxy Materials, proxy statement, the Company’s Annual Report on Form 10-K for the year ended December 31, 2025 (the “202510-K”) and proxy card/voting instruction form, as applicable, to shareholders and to employee benefit and stock purchase plan participants on April 8, 2026.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE ANNUAL MEETING OF SHAREHOLDERS TO BE HELD ON MAY 26, 2026:

The Notice of Annual Meeting of Shareholders, proxy statement and the 202510-K are available free of charge atwww.proxyvote.com.

The principal executive offices of the Company are located at 126 East Lincoln Avenue, Rahway, NJ 07065 U.S.A.

• The telephone and internet voting facilities will close at 11:59 p.m. Eastern Time on May 25, 2026.

** You will need the 16-digit control number included on your proxy card, voting instruction form or Notice of Internet Availability of Proxy Materials.

If your shares are held in a stock brokerage account or by a bank or other nominee, your ability to vote by telephone or over the internet depends on your broker’s voting process. Please follow the directions provided to you by your broker, bank, or nominee.

Dear Fellow Shareholders,

In 2025, we made meaningful progress transforming our portfolio and positioning our Company for success into the next decade and beyond. Guided by our purpose to use the power of leading-edge science to save and improve lives, we launched a wave of new products, advanced important clinical programs, and expanded our pipeline and portfolio through strategic business development. Momentum continues to build, and I am increasingly confident we have the right foundation to continue to deliver breakthrough medicines and vaccines to millions of patients around the world.

Following our strong progress in 2025, we now have line of sight to a potential commercial opportunity of over $70 billion by themid-2030s coming from just a select group of our late-stage pipeline assets. This is $20 billion more than we projected just one year ago thanks in part to our business development efforts. Also underpinning this increase is the largest and most diverse pipeline in our Company’s recent history, with approximately 80 ongoing Phase 3 studies across multiple therapeutic areas and modalities. Based on our pipeline today, we see opportunity to launch over 20 potential new growth drivers — each of which holds the promise of advancing patient care, and almost all of which have blockbuster potential. A majority of the $70 billion-plus commercial opportunity stems from 10 of these potential new growth drivers alone. Of these, three have been approved already and are making a meaningful impact for patients — WINREVAIR, OHTUVAYRE and ENFLONSIA — and the remaining ones are anticipated to readout key study data over the next 12 to 18 months, representing important catalysts for their development and clinical outlook.

In oncology, we are continuing our relentless work to deliver new treatment options for patients with cancer. We were pleased that the U.S. Food and Drug Administration (FDA) approved KEYTRUDA QLEX, which enables

subcutaneous administration of the medicine in KEYTRUDA across all solid tumor indications, and that the European Commission (EC) also approved the subcutaneous route of administration for KEYTRUDA across all adult indications in Europe. This innovation provides an important new option for patients, and we believe it further expands access to KEYTRUDA and reinforces its foundational role in the treatment of certain cancers. We also achieved important clinical milestones, with data readouts in new tumor types and earlier stages of disease for KEYTRUDA as well as WELIREG, our HIF-2 alpha inhibitor. In addition, we are progressing sacituzumab tirumotecan(sac-TMT), an investigational anti-TROP2 antibody-drug conjugate being developed in collaboration with Kelun-Biotech, which we’re evaluating in 17 Phase 3 trials. The FDA awardedsac-TMT a priority review voucher under the Commissioner’s National Priority Voucher (CNPV) pilot program, for use when our future application is submitted.

In cardiometabolic and respiratory, we are also pleased that enlicitide, our investigational oral PCSK9 inhibitor for the treatment of adults with high LDL cholesterol, was also awarded a CNPV. Positive results from three Phase 3 trials underscore the potential of enlicitide to be the first approved oral PCSK9 option to help address the cardiovascular (CV) epidemic. Additionally, since its launch in 2024, WINREVAIR has proven to be an important medicine for a broad spectrum of adults with pulmonary arterial hypertension (PAH). And OHTUVAYRE, obtained through our acquisition of Verona Pharma, provides afirst-in-class maintenance treatment for adults with chronic obstructive pulmonary disease (COPD).

In vaccines and infectious diseases, we were proud to launch ENFLONSIA in the U.S., the first and only respiratory syncytial virus (RSV) preventive option administered to infants during their first RSV season without the need for weight-based dosing. And, we continue to see increased uptake of our adult pneumococcal vaccine, CAPVAXIVE, given its strong clinical profile. We also continue to have positive data readouts from our HIV pipeline, including for our investigational once-daily, oral, two-drug, single-tablet regimen doravirine/islatravir for the treatment of HIV-1 infection. We believe islatravir has the potential to serve as a novel anchor medicine that will provide the basis for new daily and weekly treatment options for adults living with HIV. In addition, we initiated Phase 3 trials for our investigational, once-monthly oral candidate for HIV-1 pre-exposure prophylaxis (PrEP), alimatravir (also known as

MK-8527). Lastly, GARDASIL and GARDASIL 9 remain important products for preventing certain HPV-related cancers in males and females. We are proud of these as well as our other vaccines and the role they play in supporting public health.

Expanding our pipeline has been a priority, and we are making progress across multiple additional therapeutic areas. In immunology, we broadened our clinical development program for tulisokibart, our TL1A monoclonal antibody, with the initiation of Phase 2b trials in three additional inflammatory disease indications beyond the ongoing Phase 3 trials in ulcerative colitis and Crohn’s disease. In ophthalmology, we are advancing MK-3000, our Wnt agonist, potentially the first new mechanism of action in two decades for patients with certain retinal diseases. We also initiated a Phase 2/3 study for MK-8748, our Tie2 agonist/VEGF bispecific, another potential treatment for certain retinal diseases.

Animal Health remains an important contributor to our growth, and we are delivering a wave of new products in large and growing markets. In 2025, we received EC approval of NUMELVI tablets for dogs, a second-generation JAK inhibitor for atopic dermatitis, and recently received FDA approval for NUMELVI. We expect to double our commercial Animal Health business from a 2024 base by themid-2030s.

Business development continues to be a core part of our growth strategy. In addition to closing the Verona Pharma acquisition in 2025, in January of this year we completed the acquisition of Cidara Therapeutics, which brought us MK-1406, a potential first-in-class drug-Fc conjugate long-acting antiviral, to help protect high-risk individuals from influenza. Since 2021, we have invested over $60 billion in business development, and we will build on our track record by moving with discipline and intention where science and value align.

In addition, we continue to build on our long-standing commitment to advancing access to health, operating responsibly and implementing strategies that protect the health of people, animals and the planet. Our medicines and vaccines reached more than 400 million people worldwide in 2025 through our commercial channels, clinical trials, voluntary licensing and product donations — a testament to the impact and reach of the critical work we do. In the U.S. between 2018 and 2024, we invested more than $80 billion in R&D and $12 billion in manufacturing. In 2025, we committed to investing more than $70 billion over the next several years to expand domestic manufacturing and R&D — not including investments associated with future business development — to drive long-term growth and strengthen the U.S. as a global leader in biopharmaceutical innovation. We continue to prioritize developing and manufacturing medicines and vaccines close to patients in the U.S. while maintaining our global presence and aligning our manufacturing to best serve patients worldwide.

Our teams made significant strides in 2025 to bring forward our next generation of growth drivers. To help continue their commercial success, we are organizing our Human Health business into an Oncology Business Unit and a Specialty, Pharma & Infectious Diseases Business Unit. This will enable us to sustain long-term leadership in oncology, while supporting a growing number of launches across an increasingly broad and diverse portfolio. As we continue our important work, my conviction is stronger than ever in the sustainable, long-term value we are positioned to deliver for patients and our shareholders.

Thank you for your continued support of our Company and our purpose. We encourage you to participate in the Annual Meeting by exercising your right to vote.

Robert M. Davis Chairman, Chief Executive Officer and President

A Message from our Independent Lead Director

Dear Fellow Shareholders,

On behalf of the Board, thank you for your investment in the Company and your continued support. I am honored to serve as Lead Director and pleased to highlight a few of the ways the Board remains committed to you through dedicated, independent oversight.

Board Oversight and Independence

As noted by our Chairman and CEO Robert M. Davis in his letter, the Company made strong progress in 2025 to bring forward its next generation of growth drivers, launching a wave of new products, advancing important clinical programs, and expanding its pipeline and offerings through strategic business development. The Company’s progress was guided by its continued focus on using the power of leading-edge science to save and improve lives, a purpose that also guides the Board in our work to oversee the Company’s affairs and fulfill our responsibilities. In 2025, leveraging our varied backgrounds, the Board engaged actively with senior leaders on a range of topics, including research and development, capital allocation, and human capital management. Most recently, the Board provided guidance in connection with leadership changes in the Company’s Human Health and Manufacturing divisions as part of regular management succession planning discussions.

Independence is central to effective governance. In my role as independent Lead Director, I am actively engaged in ensuring the Board provides independent and effective oversight, including by presiding over an executive session at every Board meeting without management present, leading the Board’s annual self-evaluation, and working with the Chairman to set Board meeting agendas. All members of our four standing committees are independent, and each committee is chaired by an independent Director who provides strong leadership and helps guide the Board’s work.

Board Composition

The Board takes a thoughtful approach to evaluating its composition and planning for succession through ongoing discussion. We work to ensure the Board collectively has the skills, experience, and perspectives necessary to oversee the Company’s current and future global business priorities and strategic initiatives. In doing so, we seek an appropriate balance of fresh perspectives and the insights of longer-tenured Directors.

Our annual self-evaluation gives Directors a formal avenue to comment on Board composition and identify opportunities to strengthen Board and committee effectiveness. Directors offer input across many areas, including core Board responsibilities, structure, priorities, and operations. Our most recent evaluation helped identify priority topics for this year — reviewing pipeline strategy and execution, the Company’s approach to digital technologies, including artificial intelligence, and assessing the changing external and regulatory environment and related risks and opportunities. It also prompted practical improvements to our Board operations, such as continuing to streamlinepre-read materials and reserve adequate time for discussion.

Shareholder Engagement

Regular communication with shareholders helps us understand your views and make well-informed, measured decisions that serve the Company’s long-term interests. The Company continued a robust, proactive shareholder engagement program in 2025 and plans to continue to do so in 2026. I joined management in several of those conversations and valued the chance to present the Board’s perspective and hear shareholders’ priorities directly. Discussions covered corporate strategy, capital allocation, risk oversight, the board evaluation process, and board composition. The Board takes investor feedback seriously and has used it to inform the Company’s policies, practices, and disclosures.

Thank you again for your investment and continued support.