He was drafted by the Montreal Canadiens in 1974 and played for their minor league affiliate until 1977, when he made his NHL debut.

[11] Lupien was the agent for an unnamed player from the Drummondville Voltigeurs who contacted him regarding sexual advances by the team's coach Jean Bégin.

[12][13] As an agent, Lupien was a vocal proponent of improving the working conditions of players in junior ice hockey.

[14] He advocated the unionization of the Canadian Hockey League,[15] and was of the opinion that it could assist in diminishing fighting at the amateur level and result in better treatment of players by their teams.

[16] In supporting the elimination of violence in hockey on all levels,[17] he recommended that coaches be sanctioned for any fights their players are involved in.

[18] Lupien also called for decreasing the number of games in a season and cutting down travel time, believing that the taxing schedule was responsible for the mounting drug usage among junior players.

[16][19][20] He alleged in December 2003 that approximately half of the players in the QMJHL used drugs, either for recreational purposes, to enhance their performance, or to sleep on long bus journeys.

[20][21] Lupien also worked as a businessman in the fast-food industry, initially purchasing a Humpty Dumpty Snack Foods before acquiring a Boston Pizza franchise in West Island.