Julian Draxler put PSG ahead and Thomas Lemar levelled for Monaco before a goal from Angel Di Maria and a double from Edinson Cavani sealed a lively encounter at Parc OL.
PSG, who trail Monaco by three points in Ligue 1 with eight games left in the season, are now unbeaten in the French League Cup since a quarter-final defeat against St Etienne in November 2012.
Unai Emery's PSG looked nothing like the team who were knocked out of the Champions League by Barcelona with an embarrassing 6-1 defeat, while Monaco's French prodigy Kylian Mbappe put on a disappointing display.
"After what happened against Barca we had to win this final," said Di Maria.
PSG midfielder Adrien Rabiot said they had a point to prove against the Ligue 1 leaders.
"We played a great game. Everybody said everywhere that Monaco were the favourites, that they were the best team in France. We showed who we were tonight," he said.
PSG, who were without injured centre back Marquinhos, started brightly.
Read the full article on eurosport.co.uk: PSG beat Monaco to lift fourth straight League Cup