But the win was costly. TFC leading scorer Danny Dichio left the game with a groin injury suffered late in the first half.
Greg Sutton, who played five seasons in Montreal before joining TFC in 2007, shut out the Impact.
Montreal had defender Stefano Pesoli sent off in the second half for a second yellow card.
The came drew 12,083 fans at Stade Saputo, which opened last week.
Toronto, Montreal and the Vancouver Whitecaps will play home-and-home series to determine the Canadian representative, which will be among 16 teams vying for eight spots in group play. Two teams from Mexico and the USA and one each from Costa Rica, El Salvador, Guatemala and Honduras earn automatic passage to the group stage of the Concacaf Champions League.