Power of Attorney for Casey Heller

Casey Heller, Chief Financial Officer of Definitive Healthcare Corp., has granted a Power of Attorney to Jonathan Paris, Maria Borda, and Christina A. Kelleher to execute and file Forms 3, 4, and 5 with the SEC on his behalf. This authorization allows the attorneys-in-fact to prepare, execute, and submit these forms in accordance with Section 16(a) of the Securities Exchange Act of 1934. The Power of Attorney remains in effect until Heller is no longer required to file these forms, revokes the authorization in writing, or any of the attorneys-in-fact are no longer employed by the company. The document was executed on July 10, 2025.