Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report on Form 10-Q of IDEAYA Biosciences, Inc. (the “Company”) for the period ended June 30, 2025 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Yujiro Hata, President and Chief Executive Officer of the Company, and I, Joshua Bleharski, Ph.D., Chief Financial Officer of the Company, hereby certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: August 5, 2025	By:	/s/ Yujiro Hata
		Yujiro Hata
		President and Chief Executive Officer
		(Principal Executive Officer)

Date: August 5, 2025	By:	/s/ Joshua Bleharski, Ph.D.
		Joshua Bleharski, Ph.D.
		Chief Financial Officer
		(Principal Financial Officer)

The foregoing certification is being furnished solely to accompany the Report pursuant to 18 U.S.C. § 1350, and is not being filed for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and is not to be incorporated by reference into any filing of the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing.