Neymar scored twice and Christopher Nkunku was also on target as PSG moved nine points clear of Saint-Etienne.
"It's unbelievable, because the preparation has been very difficult." said PSG coach Thomas Tuchel. "The team is improving all the time."
PSG host Red Star Belgrade on Wednesday night at the Parc des Princes. With that game in the hinterland, Tuchel left midfielder Marco Verratti and strier Edinson Cavani on the bench and also experimented again with a back three.
"With three games in a week, we needed tactics and a structure to play away to Nice who are very strong with the ball," said Tuchel. "We had to make sure that we ran as little as possible after the ball."
Tuchel was able to rest Cavani and reintroduce France striker Kylian Mbappé into the line-up after a three match suspension for his red card during the match against Nimes.
The 19-year-old was at the heart of his team’s second goal. Receiving a pass from Angel di Maria, he drove at the Nice defence before unleashing a shot which was deflected into the path of Nkunku who popped it into the goal.
Nice defender Christophe Hérelle conceded his team had been outplayed. “We started well but once PSG got going it was really difficult," he said. "We actually played quite well but they were simply better than us. They’ve got some brilliant players and allwe can do now is lick our wounds and get ready for the match against Toulouse.”