PSG stuttered in their bid to close out the Ligue 1 title race after a 1-1 draw with Valenciennes left them with a seven-point lead to defend over the final three games of the season.
The capital club needed a late goal from Alex to save face in a disjointed performance at the Parc de Princes, which was not helped by PSG captain Thiago Silva receiving a red card two minutes before the break after arguing with the referee.
By then the hosts were already trailing thanks to Gael Danic's 17th-minute strike, but the 10 men of PSG dug in and were duly rewarded when Alex found the net with just seven minutes left.
Substitute Bafetimbi Gomis bagged a second-half brace as Lyon maintained their push for a Champions League berth with a 3-0 victory at Nancy.
Gomis edged Remi Garde's men in front just after half-time and added the gloss to the scoreline two minutes from time after Yoann Gourcuff (79) bagged Lyon's second.
It was third-placed Lyon's third win in four matches and one which kept them three points clear of their Champions League rivals, while Nancy remain just one point above the drop zone.
Nice climbed into the top four after defeating mid-table Rennes 3-0. The visitors broke the deadlock five minutes after half-time through Dario Cvitanich and they received a further boost when Rennes lost Chris Mavinga to a red card.
Cvitanich doubled his account from the penalty spot with 19 minutes remaining and the points were wrapped up six minutes from time when Eric Bautheac added a third.
Nice also finished the match with 10 men when Nemanja Pejcinovic was dismissed for a professional foul.