Montreal (10-8-7, 37 points) won its second straight and is 4-1-2 in its past seven games. Chicago (6-14-5, 23 points) has lost three in a row -- all by shutout.
Neither side generated much in the opening minutes, with the first chance going to Montreal when Victor Wanyama headed a free kick that went just outside the right post in the 13th minute. It was their only shot attempt of the half.
The Fire had the better opportunities in the first half, getting four of their six shots on target but were once again unable to convert on their chances.
Chicago forced Montreal goalkeeper James Pantemis into a pair of saves moments apart midway through the opening half. After diving to get his hands on a header from central defender Mauricio Pineda at the top of the goal area in the 19th minute, Pantemis dived to the right to deflect Luka Stojanovic's shot from outside the box wide of the net.
Pineda had a chance to put the Fire ahead in the 33rd minute with a header from the left side but Montreal defender Rudy Camacho headed the ball away from the goal.
Chicago picked up where it left off early in the second half with a chance from Miguel Navarro from the left side in the 53rd minute but Pantemis got the reach up to deflect the ball over the net.
Romell Quioto gave Montreal a 1-0 lead in the 60th minute, on the club's first shot on target, when Djordje Mihailovic slipped it through the Chicago defense for the Honduran striker, who connected from the goal area.
Fabian Herbers scored for the Fire in the 77th minute but the goal was called back with defender Miguel Navarro flagged for offside.
Montreal doubled its lead three minutes later on an own goal by Chicago. Mathieu Choiniere eyed midfielder Ahmed Hamdi driving down the left flank but Fire defender Carlos Teran, battling Hamdi, kicked it into his own net to make it 2-0.