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.
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."
