Michel Vaillancourt took up equestrian at the age of twelve and, within a decade, had emerged as one of Canada’s top contenders in the sport. Talented as a youngster, his determination to reach the top was further strengthened after his father, who had been his coach and primary source of encouragement, died in a riding accident in 1971. He made his international debut with the Canadian national team in 1975, winning a bronze medal in the team event at that year’s Pan American Games. His next stop was the 1976 Summer Olympics where, after Alwin Schockemöhle had achieved a flawless victory, Vaillancourt found himself tied for second with Debbie Johnsey of Great Britain and François Mathy of Belgium, necessitating a jump-off. Vaillancourt set the bar high with a show that only resulted in four fault points, and neither of the other riders were able to match it. Johnsey abandoned the round after nearly crashing her horse, while Mathy suffered eights fault points to claim bronze. Having earned silver, he finished fifth in the team event alongside Jim Day, Jim Elder, and Ian Millar.
Vaillancourt continued riding for several years and won team silver at the 1979 Pan American Games. He was selected to participate at the 1980 Summer Olympics, but attended the Alternate Olympics instead after his country joined the boycott of the regular Games. There he attained a gold medal in the team event despite having to use his alternate horse. After retiring from active competition he became involved in coaching and course design and served as the team leader for the Canadian equestrian delegations to the 1994 and 1998 Summer Olympics. He was inducted into the Jump Canada Hall of Fame in 2009 and, as of 2012, remains only one of two Canadians to medal in an individual jumping event at the Olympics (the other being Eric Lamaze).