X0609 4 2026-07-01 0000354190 Arthur J. Gallagher & Co. AJG 0001589933 GALLAGHER THOMAS JOSEPH false 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 President 0 Common Stock 2026-07-01 4 M 0 351.945 229.57 A 323743.025 D Common Stock 62295 I By grantor retained annuity trust Common Stock 96709 I By Irrevocable Trust Common Stock 31988 I By wife Common Stock 119703 I By wife as trustee Common Stock 491.14 I Gallagher 401(k) plan account Notional Stock Units 0 2026-07-01 4 M 0 351.945 0 D Common Stock 351.945 13345.6345 D Non-qualified Stock Option 127.90 2028-03-16 Common Stock 32895 32895 D Non-qualified Stock Option 86.17 2027-03-12 Common Stock 31340 31340 D Non-qualified Stock Option 228.20 2033-03-01 Common Stock 22219 22219 D Phantom Stock Common Stock 20280.735 20280.735 D Non-qualified Stock Option 158.56 2029-03-15 Common Stock 15310 15310 D Non-qualified Stock Option 243.54 2031-03-01 Common Stock 15070 15070 D Non-qualified Stock Option 337.74 2032-03-01 Common Stock 14876 14876 D Non-qualified Stock Option 177.09 2030-03-15 Common Stock 12744 12744 D The reporting person disclaims beneficial ownership of these shares, and this report shall not be deemed an admission that the reporting person is the beneficial owner of these shares for purposes of Section 16 or for any other purpose. These shares are held in trusts, for the benefit of the reporting person's children, of which his wife is a 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 and following the reporting person's separation from service. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. 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. Closing price of Gallagher common stock on February 28, 2025. One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. 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