He served in the Legislative Assembly of Ontario from 1980 to 1987, and was a cabinet minister in the government of Frank Miller.
Mitchell was a communication officer in the Department of National Defence before entering political life.
Mitchell was re-elected in the 1981 election, defeating Liberal Hans Daigeler and New Democrat Judy Wasylycia-Leis by an increased margin.
[2] When Frank Miller replaced Davis as Premier of Ontario on February 8, 1985, he appointed Mitchell as a minister without portfolio responsible for Science and Technology.
Coincidentally, Mitchell received his medical care at the Queensway Carleton Hospital in Ottawa, Ontario, which he had been affiliated with numerous times during his political career.