- Apr 3 KQW-AM in San Francisco CA changes call letters to KCBS
- Apr 3 WLWS (now WCMH) TV channel 4 in Columbus, OH (NBC) begins broadcasting
- Apr 4 Israel & Jordan sign armistice agreement
- Apr 4 North Atlantic Treaty Organization (NATO) treaty signed in Washington, D.C.
- Apr 4 WKRC TV channel 12 in Cincinnati, OH (ABC) begins broadcasting
- Apr 5 60 year old St Anthony's Hospital n Effingham, Illinois, catches fire, 77 people killed
- Apr 5 Fireside Theater debuts on US television.
- Apr 7 "South Pacific" opens at Majestic Theater NYC for 1928 performances
- Apr 9 UN International Court of Justice holds Albania responsible for incidents in Corfu Channel and awards Britain damages
US Masters Golf
Apr 10 13th US Masters Tournament, Augusta National GC: Sam Snead wins his first of 3 green jackets by 3 strokes over Johnny Bulla and Lloyd Mangrum
Sam Snead
- Apr 13 Basketball Association of America Finals: Minneapolis Lakers beat Washington Capitols, 77-56 to take series, 4 games to 2; BAA and National Basketball League merge later that year to create the NBA
- Apr 13 Philip S. Hench at Mayo Clinc announces discovery of cortisone to treat rheumatoid arthritis
- Apr 14 International Military Tribunal at Nuremberg's last judgment
- Apr 20 Jockey Bill Shoemaker wins his 1st race, in Albany, California
- Apr 23 Chinese Red army conquers Nanjing
- Apr 23 Courtesy mail boxes for motorists started in San Francisco
- Apr 23 Netherlands annexes Elten & Tudderen
- Apr 24 3rd Tony Awards: "Death of a Salesman" & "Kiss Me Kate" win
- Apr 25 Friedrich Durrenmatt's "Romulus der Grosse" premieres in Basel
- Apr 26 Transjordan is officially renamed the Hashemite Kingdom of Jordan
- Apr 28 Former Philippine First Lady Aurora Quezon, 61, assassinated while en route to dedicate a hospital in memory of her late husband; her daughter and 10 others also killed