X0609 4 2026-07-01 0000354190 Arthur J. Gallagher & Co. AJG 0002022545 Pesch Michael Robert false 2850 GOLF ROAD ROLLING MEADOWS IL 60008 1 Vice President 0 Common Stock 2026-07-01 4 M 0 355.801 229.57 A 44832.7289 D Common Stock 59 I By Child Common Stock 12505 I By Spouse's Trust Common Stock 491.139 I Gallagher 401(k) plan account Notional Stock Units 0 2026-07-01 4 M 0 355.801 0 D Common Stock 355.801 6134.526 D Phantom Stock Common Stock 49545.666 49545.666 D Non-qualified Stock Option 228.20 2033-03-01 Common Stock 13167 13167 D Non-qualified Stock Option 86.17 2027-03-12 Common Stock 7520 7520 D Non-qualified Stock Option 127.90 2028-03-16 Common Stock 7255 7255 D Non-qualified Stock Option 158.56 2029-03-15 Common Stock 4900 4900 D Non-qualified Stock Option 177.09 2030-03-15 Common Stock 3823 3823 D Shares held in irrevocable trust, of which his spouse is sole Trustee. Each notional stock unit represents a right to receive one share of Gallagher common stock. Portions of these notional stock units are payable to the reporting person in shares of common stock in July of 2026, 2027 and 2028 and following the reporting person's separation from service. Portions of these notional stock units are payable to the reporting person in shares of common stock in July of 2026, 2027 and 2028 and following the reporting person's separation from service. Each share of phantom stock represents a right to receive one share of Gallagher common stock. These shares represent awards under the Age 62 Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the reporting person. Participants vest in these awards when they attain age 62, or after a one-year period for participants who have attained age 61. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Grant date of 3/12/2020. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Grant date of 3/16/2021. Grant date of 3/15/2022. Grant date of 3/15/2023. This report discloses the distribution of notional stock units (representing compensation previously deferred by the reporting person in the Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan) in the form of Gallagher common stock. The timing of this distribution in July 2026 is in accordance with the terms of the Supplemental Savings and Thrift Plan and the reporting person's election at the time of deferral. /s/ Monica Norzagaray, by power of attorney 2026-07-06