THERMO FISHER SCIENTIFIC INC.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

(Rule

14a-101)

SCHEDULE 14A

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Thermo Fisher Scientific Inc.

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Notice of Annual Meeting of Shareholders and Proxy Statement 2026 Our Mission is to enable our customers to make the world

Our Mission is to enable our customers to make the world Healthier We make a positive impact on human health by providing our customers with advanced technologies and expertise to deliver breakthrough medicines and diagnostics that improve lives worldwide. Our customers rely on us to help them achieve the impossible. Cleaner We empower our customers with the tools to understand and address climate change, develop greener technologies and to help ensure the quality of air and water that sustains all life. As their partner, we are working with our customers to preserve our planet for future generations. Safer From products that detect contamination in food to instruments that help solve crimes and identify potential threats, we provide the solutions that enable our customers to protect our communities. Together, we are determined to create a safer world.

From our Chairman and CEO

Dear Fellow Shareholder,

On behalf of our entire company, thank you for your continued support of Thermo Fisher Scientific. I’m proud of what we have achieved and excited about the opportunities ahead to build an even brighter future for our company and all our stakeholders.

Everything we do begins with our Mission to enable our customers to make the world healthier, cleaner and safer. This inspires our more than 120,000 colleagues to bring their best each day because we know the work we do helps our customers to improve lives around the world.

Our success speaks to the power of our Mission and the purposeful way we manage our company. I’m very proud of what we achieved in 2025.

Excellent operational performance

Beginning with our financial results, we delivered excellent operational performance, reflecting outstanding execution by our team and active management of the company in a dynamic environment. In 2025, we increased revenue by 4% to $44.56 billion, grew GAAP diluted earnings per share (EPS) by 7% to $17.74, and grew adjusted EPS 1 by 5% to $22.87. We generated free cash flow 1 of $6.34 billion.

In terms of capital deployment, we were active and highly disciplined stewards, deploying approximately $16.5 billion in 2025. This included $13 billion committed to M&A for the acquisition of our Filtration and Separation business from Solventum as well as our agreement to acquire Clario, a leading provider of endpoint data solutions for clinical trials. We returned $3.6 billion to shareholders through stock buybacks and dividends, and we delivered 11.3% adjusted Return on Invested Capital (ROIC)1, reflecting our focus on generating attractive returns while strengthening our capabilities.

Proven growth strategy

We’ve earned our industry leadership and continue to build on it by executing a proven growth strategy that is designed to create durable value in every environment. Our strategy is comprised of three key pillars:

Throughout the year, a critical enabler of our success was our PPI Business System, which embeds continuous improvement, operational discipline and agility throughout our company. We’re amplifying the impact of PPI by increasingly integrating artificial intelligence into our way of working. This is improving our operational efficiency, enhancing the way we serve customers and strengthening our differentiated product and service offerings, ultimately further enhancing our industry leadership position.

Culture of integrity and accountability

As always, our performance is underpinned by our commitment to integrity and sound governance. 2025 was a dynamic year, and our Board actively engaged to oversee strategy, risk management and other key areas of operations. We also remain committed to ongoing shareholder engagement and to transparent disclosure. Your valuable perspectives help the Board shape our governance practices, design our compensation programs and advance long-term value creation for all shareholders.

That’s why your vote matters. This proxy statement describes the proposals to be voted on at our 2026 Annual Meeting of Shareholders. We ask that you vote for each of the Board’s nominees for director and for the Board’s recommended proposals.

Once again, thank you for your continued support of Thermo Fisher Scientific. We have extraordinary opportunities ahead, as our customers rely on us to enable the breakthroughs in science that will improve lives worldwide. With our passion to be our very best, we’ll be there to deliver on that promise – for our customers, our shareholders and our world.

Sincerely,

Marc N. Casper

Chairman and Chief Executive Officer

April 7, 2026

1 Adjusted EPS, free cash flow and adjusted ROIC are financial measures that are not prepared in accordance with generally accepted accounting principles (“GAAP”). Appendix A to this proxy statement defines these and othernon-GAAP financial measures and reconciles them to the most directly comparable historical GAAP financial measures.

Notice of 2026 annualmeeting of shareholders

Please refer to the proxy materials or the information forwarded by your bank, broker, trustee or other intermediary to see which voting methods are available to you.

Items of business

Shareholders will also consider any other business properly brought before the meeting.

By Order of the Board of Directors,

Julia L. Chen / Vice President and Secretary / April 7, 2026