[1] Undrafted, Trepanier played in the National Hockey League for the Colorado Avalanche, Mighty Ducks of Anaheim, and the Nashville Predators, appearing in 229 regular season games, scoring 12 goals and 22 assists for 34 points, picking up 252 total penalty minutes between 1998 and 2002.

After spending the entire 2003–04 season in the AHL with the Hershey Bears, Trepanier left North America to sign in Germany with Nürnberg Ice Tigers of the Deutsche Eishockey Liga during the 2004 NHL Lockout.

Pascal remained in Europe and played in the Swiss NLA with SC Bern the following season before returning to the DEL with Adler Mannheim.

Trepanier established himself within the German league as one of the premier offensive defenseman, topscoring for the Eagles defense in three consecutive seasons.

After the 2009–10 campaign, his fourth with Adler Mannheim, Pascal left as a free agent and signed a one-year contract with fellow DEL club, Krefeld Pinguine, on July 27, 2010.