- 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
Golf Major
- Apr 13 3rd NBA Championship: Minn Lakers beat Wash Capitols, 4 games to 2
- 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 15 Pope Pius XII publishes encyclical Redemptoris nostri
- Apr 16 Stanley Cup: Toronto Maple Leafs sweep Detroit Red Wings in 4 games (2nd year in a row)
- Apr 18 Republic of Ireland withdraws from British Commonwealth
- Apr 19 53rd Boston Marathon won by Gosta Leandersson of Sweden in 2:31:50.8
Event of Interest
- 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