A double from Jack McInerney and an opportunistic finish from Marco Di Vaio saw Montreal triumph, as they moved off the bottom of the Eastern Conference standings.
The Impact had only registered a loss and a draw in their previous two MLS fixtures but bounced back against the Dynamo, while their victory at Stade Saputo was their fifth in front of their own fans in their past seven home games in all competitions.
Montreal moved to 14 points for the season, climbing above Chicago Fire on games won, while the Impact finished the weekend just three points behind Houston in the East.
The hosts started brightly with early chances to Felipe Martins, Eric Miller and Matteo Ferrari but despite dominating Houston, Montreal had to wait until the 42nd minute to take the lead.
Miller pushed up from left-back and chipped a cross towards the six-yard box, where McInerney glanced his header inside the far post.
Montreal had 17 shots for the game with eight on target, while Houston tested Impact goalkeeper Troy Perkins just once from eight attempts, but the home side did not double their advantage until the 75th minute.
Substitute Justin Mapp got free on the right for Montreal and crossed to McInerney, who audaciously flicked the ball back over his shoulder to score in unbelievable fashion.
Just four minutes later, Di Vaio added a third, finishing from close range after Dynamo goalkeeper Tally Hall parried Andres Romero's shot.
That ended a tough match for Houston, who have lost five straight games in the MLS.
