The Montreal Impact will be facing a club from Costa Rica in the first stage of a home-and-home semi-final for the CONCACAF Champions League title on March 18.
The Alajuelense lost 2-1 against DC United on Wednesday but won the series 6-4 on aggregate.
Tickets to the March 18 game at the Olympic Stadium will go on sale Friday.
The Impact play the second leg of the series in Costa Rica between 7 and 9 April.
The semi-final was threatened by a possible MLS labour disruption but the two sides reached a tentative agreement Wednesday.
Rookie Cameron Porter, 21, in his first home game with the Impact, hit the target in the last minute of stoppage time Tuesday night to allow his team to qualify for the semifinals tournament for the first time in its history.
The Impact start the regular season on Saturday against DC United.
-With a file from The Canadian Press
