Mahoney played junior hockey for the Peterborough Petes and the Ottawa-Hull Canadiens from 1056-59. He then played one season for the Clinton Comets of the Eastern Hockey League and the Hull-Ottawa Canadiens of the Eastern Professional Hockey League. He retired as a player in 1960. He coached McMaster University in 1967-68 and the Adirondack Red Wings in 1982-83. In 1980-81 and 1981-82 he was an assistant coach for the Washington Capitals.