MARKETAXESS HOLDINGS 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

(Amendment No. )

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☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material Pursuant to § 240.14a-12

MarketAxess Holdings 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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25 Proxy Statement and Notice of Annual Meeting of Stockholders

MarketAxess Holdings Inc.

55 Hudson Yards, 15th Floor

New York, New York 10001

April 29, 2026

TO THE STOCKHOLDERS OF MARKETAXESS HOLDINGS INC.:

You are invited to attend the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of MarketAxess Holdings Inc. (the “Company”) scheduled for Wednesday, June 10, 2026 at 9:00 AM, Eastern Daylight Time. The Annual Meeting will be a virtual meeting of stockholders. You will be able to participate in the Annual Meeting, vote and submit your questions via live webcast by visitingwww.virtualshareholdermeeting.com/MKTX2026. The Company’s Board of Directors and management look forward to your participation.

Details of the business to be conducted at the Annual Meeting are provided in the attached Notice of Annual Meeting and Proxy Statement, which you are urged to read carefully.

We are pleased to take advantage of the U.S. Securities and Exchange Commission (“SEC”) rules that allow issuers to furnish proxy materials to their stockholders on the Internet. We believe these rules allow us to provide our stockholders with the information they need, while lowering the costs of delivery and reducing the environmental impact of our Annual Meeting. On or about April 29, 2026, we expect to mail to our stockholders a Notice of Internet Availability of Proxy Materials (“Notice”) containing instructions on how to access our Proxy Statement and Annual Report on Form 10-K for the year ended December 31, 2025 online and how to vote. The Notice contains instructions on how you can receive a paper copy of the Proxy Statement, proxy card and Annual Report if you only received a Notice by mail.

Your vote is important to us. Whether or not you plan to attend the Annual Meeting, your shares should be represented and voted. After reading the Proxy Statement, please cast your vote via the Internet or telephone or complete, sign, date and return the proxy card in the pre-addressed envelope that we have included for your convenience if you received paper copies. If you hold your shares in a stock brokerage account, please check your proxy card or contact your broker or nominee to determine whether you will be able to vote via the Internet or by telephone or how to instruct your broker to vote on your behalf.

On behalf of the Board of Directors, thank you for your continued support.

Sincerely,

Carlos M. Hernandez

Chairman of the Board of Directors

These items are more fully described in the Company’s Proxy Statement accompanying this notice.

The record date for the determination of the stockholders entitled to notice of, and to vote at, the Annual Meeting, or any adjournment or postponement thereof, was the close of business on April 13, 2026. You have the right to receive this Notice and vote at the Annual Meeting if you were a stockholder of record at the close of business on April 13, 2026. Please remember that your shares cannot be voted unless you cast your vote by one of the following methods: (1) vote via the Internet or call the toll-free number as indicated on the Notice or proxy card; (2) sign and return a paper proxy card; or (3) vote during the Annual Meeting atwww.virtualshareholdermeeting.com/MKTX2026.

By Order of the Board of Directors,

Scott Pintoff

General Counsel and Corporate Secretary

New York, New York

April 29, 2026

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