Angel Di Maria opened the scoring and Uruguay striker Cavani found the back of the net twice after the break before Blaise Matuidi added a stoppage-time goal to put PSG back into second place with 71 points from 31 games, three behind leaders Monaco who beat Angers 1-0 on Saturday.
Nice, who have played an extra game, are third on 70 points after Mario Balotelli's double gave them a 2-1 victory at Lille on Friday.
Di Maria collected Cavani's through ball in the 56th minute before beating Karl-Johan Johnsson with a delicate chip after PSG had struggled in a dull first half.
Four minutes later, Cavani was perfectly set up by Adrien Rabiot and doubled the advantage with a low shot from inside the box.
Read the full article on eurosport.co.uk: Cavani on target as PSG beat Guingamp to stay in contention