PSG had been dominating the early exchanges in the game, with Napoli struggling to gain a foothold, but the Italians managed to turn the game very quickly.
Carlo Ancelotti's side found their rhythm and suddenly PSG had no answer. Jose Callejon played a ball behind the defence from the right and Insigne was on hand to do the rest.
He lifted a smart finish over the onrushing Alphonse Areola and the away contingent in the stands went wild.
After beating Liverpool last time out, a win against PSG would give Napoli a great chance at topping what is a very competitive group.