The Columbus Crew dropped a 1-0 decision to the New York Red Bulls but won on aggregate 2-1, advancing to the MLS Cup final where they will face the Portland Timbers.
New York won the second leg 1-0 on Sunday at Red Bull Arena on a header from forward Anatole Bertrand Abang in the third minute of extra time. Columbus however won the first leg 2-0 on goals from midfielder Justin Meram and forward Kei Kamara on November 22 in Columbus.
The Crew will host Western Conference champ Portland in the championship match December 6.
The Crew won their only MLS Cup in 2008 with a 3-1 win over the Red Bulls.
The Red Bulls needed at least two goals in regulation in Sunday's match and a goal in extra time or more penalty kicks conversions to advance.
The Red Bulls had scored two or more goals in seven home games this season, but were limited to only six shots on target Sunday. The Crew finished with five shots on goal, including three from Kamara.
Argentina's Lucas Melano scored in the fifth minute of second half stoppage time to give the Timbers a draw at FC Dallas.
The Timbers won the two-leg aggregate West final matchup 5-3 after taking the opener 3-1 at home last weekend.
Nigerian Fanendo Adi opened the scoring for Portland in the 54th minute, but Dallas battled back on goals by American Ryan Hollingshead in the 68th minute and 34-year-old Panama striker Blas Perez in the 73rd minute.
Needing one more goal to level the aggregate, Dallas was denied to the finish, with Melano putting the dagger in the Texans' hopes.
"A lot of teams would have given up the next goal but we didn't. That says a lot about this team," Timbers coach Caleb Porter said.
"I couldn't be more proud of this group. It's a big moment for us and a big trophy but we want the biggest one."
Argentine midfielder Diego Valeri assisted on both Portland goals in the same stadium where he suffered torn knee ligaments last year.
"This is special for the team, the club and the people," Valeri said. "It was very difficult. They played really well. They had chances. But we fight, we work and we got this win."
No MLS team has rallied from a two-goal deficit to advance on aggregate since Kansas City in 2004.