Karl Ouimette picked a perfect time to score his first MLS goal, as the Canadian side secured a crucial home win.
The win leaves Montreal one New England loss or draw away from clinching the team's first playoff berth in just its second season in MLS.
The visitors took the lead when Kleberson took advantage of a turnover in midfield and slotted the ball through to Fabinho, and the Brazilian powered a shot past Troy Perkins high at the near post.
The Impact grabbed an equalizer in the 64th minute through the team's star man, Marco Di Vaio. The Italian turned and fired a deflected shot home for his 20th goal of the season.
With only minutes to play, Montreal grabbed the winner when Justin Mapp whipped in a free kick that found Karl Ouimette unmarked at the 6-yard box, and the homegrown defender headed home for his first MLS goal.