Significant dates in labour history.
- April 01 - Burston Strike School began in 1914 the U.K.; the 1972 Major League Baseball strike began in the U.S. and Canada; the 1980 New York City transit strike began; the U.S. Supreme Court decided NLRB v. Truck Drivers Local 449; the Federation of Unions of South Africa was founded; the Allied Pilots Association was founded; the Loray Mill strike began in the U.S. in 1929; Sol Chick Chaikin died
- April 02 - Weldon Mathis was born; Eugene Hanley was born; the 1994–95 Major League Baseball strike ended in 1995
- April 03 - Percy Wells died
- April 04 - The On-to-Ottawa Trek began in Canada in 1935; William Quesse was born; the 2006 Minor League Baseball umpire strike began in the U.S.
- April 06 - Rose Schneiderman was born; the 1905 Chicago Teamsters' strike began as the Teamsters engaged in a sympathy strike; B. T. Ranadive died
- April 07 - The U.S. Supreme Court decided Lochner v. New York; Basawon Singh (Sinha) died
- April 08 - The 1998 Australian waterfront dispute began
- April 09 - John H. Dent died; the U.S. Supreme Court decided Adkins v. Children's Hospital and Bunting v. Oregon; Chris Watson was born; President Harry S. Truman nationalizes all steel mills in anticipation of the 1952 steel strike; Natascha Engel was born; Thomas Jackson was born
- April 10 - Harold J. Gibbons was born; Dolores Huerta was born; Joseph Diescho was born; George Lippard was born; Edward J. Carlough was born; Lee Batchelor was born; Anna Walentynowicz died
- April 11 - The 1980 New York City transit strike ended
- April 12 - Tom Addison was born; the U.S. Supreme Court decided NLRB v. Jones & Laughlin Steel Corp.; the Auto-Lite strike began in 1934 in the U.S.; the Union Label Department, AFL–CIO was founded; the Memphis sanitation strike ended; the Queensland Council of Unions was founded; the Sons of Vulcan was founded
- April 13 - Henk Sneevliet died; the Laborers' International Union of North America was founded
- April 14 - Dorothy Jacobs Bellanca was born; Marvin Miller was born; Ernest Bevin died
- April 15 - A. Philip Randolph was born; Pablo Manlapit died; the American Federation of Teachers was founded; "Black Friday" occurred in 1921 in the U.K.; Aleksei Gastev died; the Trade Unions Forum was founded; Margaretta Scott was born
- April 16 - Joseph Havelock Wilson died
- April 17 - Manwel Dimech died
- April 18 - Joseph Labadie was born; R. J. Thomas died
- April 20 - Gro Harlem Brundtland was born; The Ludlow Massacre occurred in 1914 in the U.S.; the International Harvester strike of 1979–80 ended
- April 21 - The Bituminous coal miners' strike of 1894 began in the U.S.; the First Employment Contract is repealed in France in 2006
- April 22 - Frederick Nicholas Zihlman died
- April 23 - Russell Crowell was born; the Canadian Labour Congress was formed; Cesar Chavez died; the Hock Lee bus riots occurred in 1955 in Singapore; Edward Lamb was born
- April 25 - Arnold Miller was born
- April 26 - United Trade Union Centre (Lanin Sarani) was founded
- April 28 - Workers' Memorial Day; Roy Lee Williams died; Bob White was born; Greg Combet was born; Jerry Horan died; Joseph Glimco died
- April 29 - The Coeur d'Alene miners' dispute of 1899 occurred in the U.S.