He played junior hockey for the Charlottetown Royals from 1937 to 1940 and then joined the Canadian miltary for World War II. After one season with the Petawawa Army Grenades in 1940-41 he was out of hockey until 1945, In 1945-46 he played for the senior Drummondville Intrepides and in 1946-47 for the Moncton Hawks. Trainor turned pro with the St. Paul Saints in 1947-48 and got a callup to the New York Rangers in 1948-49. He scored a goal and two assists in 17 games.