Lorenzo Insigne scored a first-half penalty as the Bianconeri succumbed to their third league defeat of the campaign. After Giorgio Chiellini was penalised for a foul on Amir Rrahmani, Insigne converted the penalty with aplomb, giving Wojciech Szczesny no chance.
The visitors fought hard after the break to restore parity, but Gennaro Gattuso's side stood firm and weathered the storm.
With the win, Napoli moved back into the Champions League places, whereas Juventus are now seven points behind leaders AC Milan, who have a game in hand.
On that note, here are the five hits and flops from game at the Stadio San Paolo:
Flop: Cristiano Ronaldo (Juventus)
It was not the best night for Juventus' prolific No. 7, as Cristiano Ronaldo failed to breach a determined Napoli rearguard.
The likes of Alex Sandro and Danilo looked to find Ronaldo inside the box with crosses and even made a few defence-splitting passes, but they were mostly off-target.
The Portuguese also had chances from set-pieces, standing over two free-kicks, but squandered both of them.
Ronaldo's pressing was strong, as he made several inroads through the heart of Napoli's defence, but a goal was not to be for the Juventus superstar on the night.
Hit: Lorenzo Insigne (Napoli)
For the second time in as many years, Lorenzo Insigne condemned mighty Juventus to a defeat.
The Italian striker was on target in Napoli's 2-1 win over the Bianconeri at home last year; he netted in the 86th minute to seal all three points. He was the difference-maker once again a year later, this time from 12 yards.
Giorgio Chiellini's foul on Amir Rrahmani gave the Partenopei the chance to go ahead. Insigne stepped up and made no mistake from the spot, thumping home a strong effort into the top-right corner.
It was only his fourth goal against the Bianconeri in 18 games, but arguably one of the most important ones, as it propelled his side up to fourth in the league standings.