IDEAYA Biosciences, 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☒ Filed by a party other than the Registrant☐

Check the appropriate box:

(Name of Registrant as Specified In Its Charter)

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

Payment of Filing Fee (Check all boxes that apply):

Dear Stockholder:

I am pleased to invite you to attend the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of IDEAYA Biosciences, Inc. (“IDEAYA”), which will be held online atwww.proxydocs.com/IDYA, on June 16, 2026 at 1:30 p.m. Pacific Time.

The attached Notice of Annual Meeting of Stockholders and Proxy Statement contain details of the business to be conducted at the Annual Meeting.

Whether or not you attend the Annual Meeting online, it is important that your shares be represented and voted at the meeting. Therefore, I urge you to promptly vote and submit your proxy via the Internet, by phone or by mail. If you decide to attend the Annual Meeting online, you will be able to vote electronically or via phone using the control number on your proxy card, even if you have previously submitted your proxy.

On behalf of the Board of Directors, I would like to express our appreciation for your interest in IDEAYA.

Sincerely,

/s/Yujiro Hata

Yujiro Hata

President and Chief Executive Officer

5000 Shoreline Court, Suite 300

South San Francisco, California 94080

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON JUNE 16, 2026

To the Stockholders of IDEAYA Biosciences, Inc.:

NOTICE IS HEREBY GIVEN that the Annual Meeting of Stockholders (the “Annual Meeting”) of IDEAYA Biosciences, Inc., a Delaware corporation (the “Company”), will be held on Tuesday, June 16, 2026, at 1:30 p.m. Pacific Time. The Annual Meeting will be held entirely online in order to provide expanded stockholder access and participation, as well as improved communications. You will be able to attend and participate in the Annual Meeting online by registering atwww.proxydocs.com/IDYA. Once registered you will receive further instructions via email on how to listen to the meeting live, submit questions, and vote. The Annual Meeting will be held for the following purposes:

1. To elect three Class I directors to hold office until the 2029 annual meeting of stockholders or until their successors are elected and qualified;

2. To ratify the selection, by the Audit Committee of the Company’s Board of Directors, of PricewaterhouseCoopers LLP, as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2026;

3. To approve, on a non-binding, advisory basis, the compensation of the Company’s named executive officers as disclosed in the Proxy Statement accompanying this Notice of Annual Meeting of Stockholders; and

4. To transact such other business as may properly come before the Annual Meeting or any adjournment or postponement thereof.

The foregoing items of business are more fully described in the Proxy Statement accompanying this Notice of Annual Meeting of Stockholders. Only stockholders who owned common stock of the Company at the close of business on April 20, 2026 (the “Record Date”) can vote at this meeting or any adjournments that take place.

The Board of Directors recommends that you vote as follows on the matters to be presented to stockholders at the Annual Meeting:

1. FORthe election of the director nominees named in Proposal 1 of the Proxy Statement, to hold office until the 2029

annual meeting of stockholders or until their successors are elected and qualified;

2. FORthe ratification of the selection of PricewaterhouseCoopers LLP as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2026, as described in Proposal 2 of the Proxy Statement; and

3. FORthe advisory vote to approve the compensation of the Company’s named executive officers, as described in Proposal 3 of the Proxy Statement.

YOUR VOTE IS IMPORTANT. WHETHER OR NOT YOU PLAN TO ATTEND THE ANNUAL MEETING ONLINE, WE ENCOURAGE YOU TO READ THE ACCOMPANYING PROXY STATEMENT AND OUR ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED DECEMBER 31, 2025, AND SUBMIT YOUR PROXY AS SOON AS POSSIBLE USING ONE OF THE THREE CONVENIENT VOTING METHODS DESCRIBED IN THE “INFORMATION ABOUT THE PROXY PROCESS AND VOTING” SECTION IN THE PROXY STATEMENT. IF YOU RECEIVE MORE THAN ONE SET OF PROXY MATERIALS OR NOTICE OF INTERNET AVAILABILITY BECAUSE YOUR SHARES ARE REGISTERED IN DIFFERENT NAMES OR ADDRESSES, EACH PROXY SHOULD BE SIGNED AND SUBMITTED TO ENSURE THAT ALL OF YOUR SHARES WILL BE VOTED.

By Order of the Board of Directors

/s/ Yujiro Hata

Yujiro Hata

President and Chief Executive Officer

South San Francisco, California

April 29, 2026

TABLE OF CONTENTS

5000 Shoreline Court, Suite 300

South San Francisco, California 94080

PROXY STATEMENT