At the 1980 Summer Paralympics in Arnhem, Netherlands, he competed in both track and swimming, winning gold medals in the men's 100-metre sprint, javelin and 100-meter backstroke, a silver medal in the 100-metre breaststroke, and a bronze medal in the 100-metre freestyle.
Lapalme competed on the men's wheelchair basketball team at both the 1988 Summer Paralympics in Seoul, South Korea and the 1992 Summer Paralympics in Barcelona, Spain. but the team did not medal at either event.
Following the end of his Paralympic career he was cast in his first acting role, as Jerome of Sandy Cove in Phil Comeau's 1994 film Jerome's Secret. He subsequently had small parts in the films Bleeders and Two Lovers and a Bear, and an episode of the television series F/X: The Series.
- Robert Lagacé, "Denis Lapalme heureux d'avoir vécu dans le «secret» sur grand écran". L'Acadie Nouvelle, October 13, 2015.
- Randy Phillips, "Lapalme leads way to Defi crown". Montreal Gazette, May 5, 1997.
- Rick Mayoh, "Strong Canadian team in medal chase at Seoul Paralympics". Ottawa Citizen, October 15, 1988.
- "Paralympic gold for Regina racer". Edmonton Journal, September 9, 1992.
- "Bronze for Canada". Edmonton Journal, August 12, 1990.
- "Canadians add gold in Stoke Mandeville". The Globe and Mail, September 1, 1979.
- "Diverse mix of players produces winning formula for Ottawa Sledgehammers". Toronto.com, April 21, 2011.
- "The Acadian Tale About A Mysterious Amputee". Canada AM, March 30, 1995.