It was the Impact's (1-4-3) first win since a 2-1 decision over Philadelphia on Oct. 19 last season.
Philadelphia (1-3-5) is winless in its last seven games.
Felipe got his second goal of the season in the 15th minute when Patrice Bernier stole the ball from Sheanon Williams and took a long shot that Zac MacMath blocked, only to fee the Brazilian bang in the rebound.
It was Montreal's first home game on the grass field at Saputo Stadium - after playing three times indoors at Olympic Stadium - but the stands were only half full in chilly, wet weather even though the team announced Friday that 18,000 tickets were sold.
It was the first meeting between the teams since the Impact sent Andrew Wenger to the Union for Jack McInerney in a swap of strikers three weeks ago.