Fabio Quagliarella, Marek Hamsik and Ezequiel Lavezzi struck in the second half to cancel out Giorgio Chiellini's early strike and hand Juventus their third straight defeat in all competitions.
Victory lifted Napoli level with Juve on 45 points, three behind Palermo in the fourth spot which would claim a place in the Champions League preliminaries.
Centre back Chiellini headed Juve in front on seven minutes after captain Alessandro Del Piero had nodded on a free-kick from the right.
Hamsik got on the end of a Quagliarella cross to equalise in the 50th minute and make amends for having smacked a penalty on to the crossbar.
The Slovak midfielder returned the favour by floating the ball to the far post for Quagliarella to score in the 72nd, although Juve keeper Alex Manninger probably should have intercepted it.
Unmarked Argentine forward Lavezzi poked in two minutes from time to make sure the visitors went down again after a 1-0 loss to Sampdoria and last week's 4-1 drubbing at Fulham in the Europa League.
Juventus's wretched luck with injuries also continued as midfielder Christian Poulsen limped off.
"At the moment we can't take certain rhythms," Juve coach Alberto Zaccheroni told Sky television.
"We had some players coming in after a period of inactivity, we lacked the ability to pressure Napoli consistently in midfield.
"To achieve my objectives I need the means to do it with. We must stop this haemorrhage of injuries."
With eight games to go, leaders Inter Milan are four points ahead of AC Milan and AS Roma, who they visit on Saturday, after beating bottom side Livorno 3-0 on Wednesday.
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