Four-time Clausura champions Sporting Cristal drew 1-1 at Los Caimanes on the 15th and final matchday on Sunday.
Three second-half goals, headlined by Mauro Guevgeozian's 87th-minute winner, saw 10-man Alianza Lima edge fourth-placed Melgar 3-2.
Both Sporting Cristal and Alianza Lima tallied 33 points, meaning a title play-off at a neutral venue will be played on Wednesday to crown the Clausura champion.
The winner of the match will then meet Apertura champions Juan Aurich for the national championship.
Union Comercio ended the Clausura campaign in third position - five points adrift of the top two - after accounting for lowly Cienciano 3-0.
Santiago Silva netted a hat-trick as second-bottom Universidad San Martin humiliated cellar-dwelling San Simon 6-0.
Luis Perea also scored twice for Universidad San Martin, while Yhirbis Cordova bagged the home team's third goal of the game.
Inti Gas made light work of Leon de Huanuco, winning 5-2 to end a run of consecutive defeats.
Universitario came from behind to beat Juan Aurich 3-1, lowly UTC Cajamarca were winners over Sport Huancayo by the same scoreline, while Real Garcilaso claimed back-to-back victories thanks to a 2-1 triumph against Cesar Vallejo.
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