- Kylian Mbappé (29', 87')
- Terem Moffi (21', 68')
- Gaëtan Laborde (53')
PSG, who on Tuesday host Borussia Dortmund in the Champions League, could have provisionally topped the standings with a win but slipped down to third on eight points.
"Nice were a very difficult team, with a very attractive game plan," coach Luis Enrique said.
"Physically, I think they were superior to us and then they were very good in all counterattack situations."
PSG were in control in the first half and Ousmane Dembélé struck early towards the top far corner only to be denied by Nice keeper Marcin Bulka, seconds after Kylian Mbappé was blocked inside the box.
But the game saw a quick turnaround when Moffi put Nice in front in the 21st minute, netting low inside the near post.
The visitors' joy lasted just under 10 minutes, though, and Bulka could only claw at the ball when Mbappe smashed it in from the edge of the box to draw PSG level just before the half-hour mark.
The Parisians regained the momentum and could have earned the lead before half-time when Dembele sent a pass across the face of the goal but Mbappe was late to bundle it into the net with a sliding tackle.
Instead, forward Gaëtan Laborde restored the lead for Nice after the break from close range, capitalising on an excellent ball control and a pass from tight angle by Moffi.
Gianluigi Donnarumma saved the hosts from conceding a quick third when Sofiane Diop took a chance from close range, but the PSG keeper was powerless when Moffi tricked the PSG defense to make it 3-1 with a low shot in the 68th minute.
Mbappe restored PSG's hopes when he got on the scoresheet again three minutes from time with a shot that bounced off the ground before making it inside the far post.
The hosts stormed Nice's box in stoppage time but lacked time and precision to rescue a draw.
"It was a great Nice team in front of us," substitute Randal Kolo Muani said. "They managed to keep calm, play their football and then score goals."
PSG did not lose any of their previous 13 home matches against Nice in all competitions.
Nice, meanwhile, are one of four teams still unbeaten in the top-flight this season, along with Rennes, Marseille and Monaco.
- Clément Turpin
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