Bobby Boswell also scored to help the Dynamo (9-5-7) win their third straight and move into third place in the Eastern Coference. Kandji had his first two-goal game since Oct. 24, 2009, when he was playing for New York.
Montreal (7-13-3) has lost two of three and five of its last seven.
Kandji put the Dynamo up 1-0 in the seventh minute, knocking in the rebound of his own shot off Montreal goalkeeper Donovan Ricketts and Zarek Valentin and inside the far post.
Houston nearly doubled its lead in the 12th minute but Andre Hainault was whistled offsides before his shot from eight yards out on the right box dribbled inside the far post.
Kandji had an open net on a breakaway in the 65th minute after Hainault played him a through ball and Kandji headed it past Ricketts, but Shavar Thomas saved the goal with a tackle from behind in front of the net to keep Houston's lead at 1-0.
Boswell extended the Dynamo's lead in the 84th minute with a header from inside the 6-yard box to just inside the far post off Brad Davis' corner kick. Kandji capped the scoring in the 89th minute.
Montreal was on the attack early with Lamar Neagle having his header ricochet off the post in the second minute and Davy Arnaud had a shot go wide from outside the box in the fourth.
Sanna Nyassi missed a chance to it at 1-1 in the 79th minute when his shot from 10 yards out in the left box stayed wide of the near post.
- Macoumba Kandji
- Montreal Impact
- Bobby Boswell
- Donovan Ricketts