He played junior hockey for the Fort William Kams from 1932 to 1936. In 1936-37 MacKay went to the New York Rovers and played there for four seasons. The New York Rangers signed him as a free agent in 1940 but he only played for their farm team the Philadelphia Ramblers in 1940-41. He was traded to the Buffalo Bisons the following season.
From 1942 to 1945 he played for senior teams in Canada. From 1945 to 1949 he split his time between the Buffalo Bisons and the Montreal Canadiens. Over the four seasons MacKay played in 19 NHL regular season games, scoring 3 assists and in 15 playoff games, scoring 1 goal and 2 assists. He went back to the Bisons in 1949-50 and then played for the Cleveland Barons in 1950-51.
MacKay finished off his career with the Quebec Aces in 1951-52 and 1952-53.