Mickey Hennessy was a Quebec provincial boxing champion during the 1930s and was selected to represent Canada in the flyweight division at the 1936 Summer Olympics. Along with middleweight Irving Pease, however, he was one of two Canadian boxers at the Games who failed to make their weight and were thus unable to participate. He retired in the 1940s and maintained a low profile until 1952, when he moved to Fort William, Ontario and took over as head coach of the Fort William Canadians, a junior ice hockey team. He held this position for 12 seasons, collecting numerous regional titles, and was a scout for the Montreal Canadiens of the National Hockey League until 1978. It was during this time that he began to realize his political ambitions, earning a seat on the Fort William city council in 1962 and holding it until 1969, when it amalgamated with several other towns to form Thunder Bay. He spent seven more years as a member of the new council prior to his election to the Legislative Assembly of Ontario in 1977. He served in this capacity for a decade until he was unseated in the 1987 Ontario general election. He returned to the Thunder Bay city council and sat there until his death in March 1991. He was inducted into the Canadian Boxing Hall of Fame in 1977 and the Northwestern Ontario Sports Hall of Fame in 1994.