Sfiane Diop and Guillermo Maripan scored a goal in each half against the home team to seal the win and stretch their win to stretching their unbeaten run to 11 games.
Monaco had already beaten the Parisians at home in November and they went in front here in the sixth minute when Ruben Aguilar knocked down Kevin Volland's cross for Diop to head in.
The home side failed to muster a shot on target in the first half and they continued to lack inspiration after the break, as Monaco doubled their lead in the 51st minute.
Monaco became the first team to beat PSG twice in the same Ligue 1 season since Nancy in 2011/12. They are in fourth place in the domestic standings, within two points of PSG who are in third.
Lille currently leads the standings three points ahead of Lyon after registering a convincing 4-1 win over Lorient.
Jonathan Ikone scored a hat-trick in Lille's win.
On Friday, Lyon beat Brest 3-2 to keep the pressure on Lille.
(with AFP)
