It was a third defeat in their last four league games for PSG, who also let a two-goal lead slip in Saturday’s French Cup final before losing to Stade Rennes on penalties.
PSG, who secured the Ligue 1 title earlier this month, remain 16 points ahead of second-placed Lille despite the latest setback.
PSG and Montpellier exchanged own goals in the first half before Angel di Maria put the visitors 2-1 ahead just after the hour mark.
Yet Andy Delort equalised after a quick attack launched from the back by Montpellier with 11 minutes left before a horror defensive error allowed the hosts to steal the ball and 36-year-old Camara’s shot was deflected in to win the game with time running out.
Montpellier moved into fifth place, five points behind St Etienne in fourth .
(Reporting by Mark Gleeson; Editing by Toby Davis)
