Pearce joins a Montreal side with major question marks surrounding a defense that lost Alessandro Nesta to retirement and surrendered 49 goals in 2013.
Pearce is coming off hip surgery to repair an injury that had hampered him over the course of two seasons, limiting the ability that made him an MLS All-Star in 2012.
Capable of playing left back or central defender, Pearce projects to be a starter for Montreal assuming he has fully recovered from the surgery that cost him the second half of the 2013 MLS season with the Red Bulls. Pearce was limited to 14 matches for the Red Bulls last season before parting ways with the club after his contract expired.
"Having played over 100 games in this league, his experience and soccer savvy will bring a lot to the team," said Impact Sporting Director Nick De Santis in a club release. "He is a natural left back, who will give us more depth on defence and who can contribute to the offence as well. Heath is highly motivated to get back to the level that saw him on the national team at one point in his career."
Pearce, 29, has made 35 appearances for the U.S. national team.