After a Philadelphia corner kick, the ball bounced outside the box and Fabinho fired a shot that goalkeeper Evan Bush stopped but couldn't control. Edu was able to settle the ball and strike home the tying goal.
Eric Ayuk Mbu gave Philadelphia (5-10-4) a 1-0 lead, one-timing a shot from the top of the penalty box in the eighth minute.
Montreal (5-6-3) tied it when Ignacio Piatti right-footed a shot from outside the box into the bottom right corner.
Former Union forward Jack McInerney put the short-handed Impact ahead just minutes after Patrice Bernier was sent off after getting a second yellow card.
McInerney settled a pass from Andres Romero at the top of the box and fired a shot into the bottom right corner.