The result leaves PSG still waiting for their first league win of the campaign after three matches, while Monaco maintained their perfect record under Filipe Luis with a third straight victory.
PSG had already been forced to come from behind to draw their opening two league games, and they again looked vulnerable early on. They had led at half-time in only one of their previous six Ligue 1 matches.
Desire Doue almost broke the deadlock after 12 minutes when his pass released Achraf Hakimi. The defender's shot was blocked, with the ball falling back to Doue, but Lukas Hradecky produced an excellent save. Khvicha Kvaratskhelia then fired the rebound over.
PSG eventually found a breakthrough just after the half-hour mark. Kvaratskhelia delivered a dangerous cross from the left and Marquinhos got the final touch, directing the ball into the net with his chest.
The hosts continued to create chances, with Kvaratskhelia forcing another good save from Hradecky before Monaco finally tested PSG shortly before half-time. Paris Brunner, however, pulled his shot wide.
PSG continued to control much of the second half, but Monaco suddenly found a way back into the game.
Jordan Teze floated a cross into the box shortly before the hour and Nazinho rose to head the ball past Matvey Safonov. It was Monaco's first shot on target of the match.
PSG pushed for a response, but Monaco delivered another blow with 18 minutes remaining.
Aleksandr Golovin appeared ready to shoot from distance before slipping a pass into the path of Stanis Idumbo. The forward took his chance from a tight angle on the left and beat Safonov at his near post.
PSG thought they had rescued another draw late on when Ferran Torres found the net, but the goal was ruled out for offside.
Monaco held on to complete a third consecutive victory over PSG in Ligue 1. It is the first time since the club's Qatari takeover that PSG have lost three league meetings in a row against the same opponent.
The champions have now gone four Ligue 1 matches without a win, their longest such run since 2023.
PSG will now turn their attention to Europe when they host SK Slovan Bratislava in the Champions League on Wednesday, hoping to put their troubled domestic start behind them.
Luis Enrique has played down Paris Saint-Germain's poor start to the Ligue 1 season, insisting there is no reason for concern despite the champions taking just two points from their opening three matches.
Ferran Torres has revealed that his decision to leave Barcelona for Paris Saint-Germain was made well before his European summer transfer, with the forward admitting he was eager to join the European champions.
Paris Saint-Germain coach Luis Enrique believes Bradley Barcola's move to Liverpool was the right decision for everyone involved, despite the French winger leaving the European champions after two important seasons.
Folarin Balogun pulled out of a proposed move to Everton after becoming unhappy with the way the Premier League club handled his medical, according to AS Monaco managing director Thiago Scuro.
