Pronovost was with the Montreal Canadiens as a practice goaltender in the 1955–56 season when he played his first NHL game. On January 14, 1956, the Boston Bruins arrived to play in Montreal. The Bruins were without regular starter Terry Sawchuk and were unable to use their back up John Henderson because of equipment problems. The Canadiens loaned Pronovost to the Bruins for the game. He made 31 saves and he recorded a shutout against his own team in a 2-0 Bruins win. He was also assessed a delay of game penalty.
Pronovost's hockey career lasted from 1952 to 1963. He spent most of his time playing in various minor professional leagues, including the Quebec Hockey League and the Eastern Professional Hockey League. The only other time Pronovost played in the NHL was during the 1958–59 season, when he played two games for Montreal.