Arnold H. Koonin, 81, of Potomac, MD passed away peacefully on August 20, 2025. Arnold is survived by his beloved wife of 55 years, Gloria Koonin, his devoted children Adam (Karen) Koonin, and Andrea (Neal) Rosenthal, his cherished grandchildren Laura, Ryan, Caleb, and Reese, along with numerous nieces, nephews, and cousins. A native Washingtonian and graduate of Woodrow Wilson High School. He received his undergraduate degree from Marquette University, and earned his law degree from Georgetown University. Arnie dedicated almost 40 years of his career as a respected tax attorney with PricewaterhouseCoopers before continuing to share his expertise as a financial advisor with Morgan Stanley for 20 years. Whether he was at work or with family he was the problem solver, trusted advisor, revered mentor, and friend and confidante to all. He was an avid fan of Washington sports teams, a car enthusiast, and a lover of tennis. Above all, Arnie loved traveling the world with Gloria, and spending his summers basking in the sun with family and friends in Bethany Beach. A funeral service will be held on Sunday August 24th at 10:30 am at Kol Shalom Synagogue, 9110 Darnestown Road, Rockville, MD 20850, followed by a graveside service at 12 p.m. at Judean Memorial Cemetery, 16225 Batchellors Forest Road, Olney, MD 20832. Shiva will take place at the Koonin residence Sunday, Monday, and Tuesday from 6 to 8 p.m. with minyan services 6:30 p.m. Charitable donations in Arnie's honor can be made to St. Jude's Children's Hospital and The Barker Foundation .

St. Jude Children's Research Hospital
501 St. Jude Place, Memphis TN 38105
Tel: 1-800-805-5856
Web: http://www.stjude.org/

The Barker Foundation
Web: https://www.barkeradoptionfoundation.org/