Exhibit 99.1 NEWS RELEASE ARTHUR J. GALLAGHER & CO. ANNOUNCES FIRST QUARTER 2025 FINANCIAL RESULTS ROLLING MEADOWS, IL, May 1, 2025 — Arthur J. Gallagher & Co. (NYSE: AJG) today reported its financial results for the quarter ended March 31, 2025. Management will host a webcast conference call to discuss these results on Thursday, May 1, 2025 at 5:30 p.m. ET/4:30 p.m. CT. To listen to the call, and for printer-friendly formats of this release and the "CFO Commentary" and "Supplemental Quarterly Data," which ...