Peter Trainor was born in Cockermouth, Cumberland in 1915. He began his football career with Workington of the North Eastern League and joined Preston North End in 1937, but never played for their first team. He moved on to Brighton & Hove Albion a few months later, and soon established himself in the team, but the outbreak of the Second World War and consequent abandonment of competitive football for the duration meant he was into his thirties before the resumption. He played occasionally at centre forward after the war, but then lost his place entirely and went back to Workington at the end of the 1947–48 season.
Peter played 94 matches for the Seagulls between 1938 and 1948 scoring 5 goals.