After Toronto's wild 3-2 win over the Montreal Impact in Wednesday's second leg forced extra time , it was substitutes Benoit Cheyrou and Tosaint Ricketts who scored to give TFC the 7-5 aggregate triumph.
Toronto now will host the MLS Cup final Dec. 10 at BMO Field against the Western Conference champion Seattle Sounders.
Armando Cooper, Jozy Altidore and Nick Hagglund scored in regulation for Toronto to make it 5-5 on aggregate through 180 minutes, while goals from Dominic Oduro and Ignacio Piatti allowed Montreal to draw level 2-2 on the away-goals tiebreaker.
TFC appeared to suffer a major blow in extra time when reigning MLS MVP Sebastian Giovinco — who had two assists in regulation — departed with an apparent muscle injury in the 107th minute.
But Cheyrou came off the bench for his first appearance since the knockout round and nodded home a Steven Beitashour cross a minute later, sending BMO Field into euphoria.
Toronto doubled the advantage two minutes later, as Altidore made a bulldozing run down the right flank and found Ricketts for the finish from close range.
The MLS Cup final will cap a remarkable run from TFC, which had never won a playoff game before ousting the Philadelphia Union in the knockout round and rolling to a 7-0 aggregate triumph over New York City FC in the conference semifinals.