Born Michael Andrew Fox in Edmonton, Alberta, Canada, he adopted the J as a homage to character actor Michael J. Pollard. He has written an autobiographical book, called Lucky Man, about his experience of young-onset Parkinson's disease.
Notable roles include the Back to the Future films, and the TV series Family Ties and Spin City. He is the voice of Stuart Little in the series of movies based on the popular book by E.B. White. He has recently created a pilot for a sitcom series entitled Hench at Home.