He headed west in his late teens with the hope of finding work as an actor in Toronto. Small roles in theatre and some work in television was enough to keep him going. Of particular note was an appearance in a live production of Romeo and Juliet opposite Genevieve Bujold for CBC. To further his career he also attended the renowned Actors Studio in New York, but it was his work in a National Film Board historical documentary short that brought him to the attention of executives at Universal Studios in 1965. Sarrazin was one of the last actors to work under what used to be called "the studio system."

He appeared in a handful of forgettable productions for the first two years of his contract but began to be noticed when he was cast opposite singer-actor Bobby Darin in Gunfight in Abilene and then as the reluctant apprentice to George C. Scott in The Flim-Flam Man, also made in 1967. The following year, 1968, he appeared in Journey to Shiloh and was nominated for a Golden Globe Award for his work in The Sweet Ride, which costarred Jacqueline Bisset. They would remain together for another 14 years.

It is safe to say the highlight of his career came in the wonderfully shot, beautifully told They Shoot Horses, Don’t They? Paired with Jane Fonda in a film set in the hard times when people would do almost anything to earn a few dollars, They Shoot Horses, a film about marathon dancing contests, was nominated for nine Oscars, but only picked up a single award when Gig Young won for best supporting actor. However the film brought Sarrazin a BAFTA nomination for most promising newcomer.

Sarrazin went on to appear in the critically successful Sometimes a Great Notion, playing the misunderstood half-brother to Paul Newman. Other films in his career include The Life and Times of George Roy Bean in 1972 and perhaps the best underrated road movie ever made, the wildly weird The Gumball Rally in 1976.

While almost all of his work was south of the border he did return home to work on Joshua Then and Now in 1985 and in the 1993 Golden Reel Award-winning film La Florida, produced by his brother Pierre Sarrazin. He had a recurring role in the short-lived Canadian series, The City (1999–2000), for which he received a Gemini Award nomination for best performance by a supporting actor in a series. Other notable films include The Groundstar Conspiracy (1972), For Pete’s Sake (1974), The Reincarnation of Peter Proud (1975), The Loves and Times of Scaramouche (1975), Deadly Companion (1986), Captive Hearts (1988), The Peacekeeper (1996), and Fear Dot Com (2002).

A service for Michael Sarrazin is planned at St. Patrick’s Basilica in Montréal on April 26 at 10:30 a.m.