On September 11, 1952, the Maple Leafs traded Mortson along with Ray Hannigan, Al Rollins and Cal Gardner in exchange for Harry Lumley. Mortson played 6 seasons for the Black Hawks and he led league in penalty minutes for the fourth time in the 1956–57 season. On September 3, 1958, the Black Hawks traded him to the Detroit Red Wings for future considerations. He retired from playing professional ice hockey in 1967. He played in 8 NHL All-Star games.