X0508 4 2026-03-01 0000354190 Arthur J. Gallagher & Co. AJG 0001929606 Gallagher Patrick Murphy 2850 GOLF ROAD ROLLING MEADOWS IL 60008 1 Chief Operating Officer 0 Common Stock 2026-03-03 4 M 0 5000 79.59 A 36442.6637 D Common Stock 10560 I By Spouse as Trustee Common Stock 418.696 I Gallagher 401(k) plan account Common Stock 53112 I By Spouse's Trust Common Stock 83407.25 I By Trust Common Stock 20432 I By Trust Common Stock 54959 I By Irrevocable Trust Non-qualified Stock Option 228.20 2026-03-01 4 A 0 17775 0 A 2033-03-01 Common Stock 17775 17775 D Non-qualified Stock Option 79.59 2026-03-03 4 M 0 5000 0 D 2026-03-14 Common Stock 5000 0 D Phantom Stock Common Stock 16052.856 16052.856 D Non-qualified Stock Option 337.74 2032-03-01 Common Stock 11901 11901 D Non-qualified Stock Option 243.54 2031-03-01 Common Stock 11386 11386 D Non-qualified Stock Option 127.90 2028-03-16 Common Stock 7255 7255 D Non-qualified Stock Option 86.17 2027-03-12 Common Stock 6270 6270 D Non-qualified Stock Option 177.09 2030-03-15 Common Stock 6160 6160 D Non-qualified Stock Option 158.56 2029-03-15 Common Stock 5510 5510 D Phantom Stock Common Stock 3804.562 3804.562 D Shares held in trusts, for the benefit of the reporting person's children, of which his wife is sole trustee. Shares held in a revocable trust and an irrevocable trust of which the reporting person's spouse is sole Trustee and as to which he disclaims beneficial ownership Shares held in trust for the benefit of the reporting person's children, of which he is a trustee. One-third of this stock option becomes exercisable 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. Grant date of 3/14/2019. 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. 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. Grant date of 3/16/2021. Grant date of 3/12/2020. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Grant date of 3/15/2022. These shares represent awards under the Deferred Cash Participation Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the participant. These awards are payable in a lump sum on the six-month anniversary of the reporting person's separation from service. Ex-24: Power of Attorney. /s/ Monica Norzagaray, by power of attorney 2026-03-03