Napoli squandered the chance to move to within a point of Serie A leaders Roma as a late Antonio Cassano goal was sufficient to guide Parma to a shock 1-0 victory on Saturday night.
Cassano struck with a fine goal nine minutes from full-time as Parma claimed just their fourth win of the season.
It was Napoli's second successive defeat, though, following the emphatic defeat by Juventus last time out.
It was an even match with both sides showing attacking intent from the outset.
Parma were first to show with Cassano finding Nicola Sansone in the area who shot wide.
Rafael Benitez's side then chanced their arm when Gonzalo Higuain fired in a right-footed shot from the centre of the area which was saved by Antonio Mirante.
Sansone fired another effort wide, this time from close range following a wonderful ball from Mattia Cassani.
Napoli then had two quickfire efforts. Lorenzo Insigne's curling shot from the edge of the area went inches wide of the far post before Higuain was again denied by Mirante from close range.
Napoli goalkeeper Pepe Reina went down to save Marco Parolo's 35-yard drive in the corner before Goran Pandev fired over for the hosts with the last effort of the first half.
The second half started where the first left off with both sides attacking.
Cassano's cross from the right found Felipe Dal Bello in the middle of the penalty area and his shot skimmed the bar before Parolo then headed over Cassani's cross.
Parma were again indebted to Mirante, who saved well in the top right-hand corner from Lorenzo Insigne's free-kick from the edge of the area.
Reina then easily gathered Parolo's long-range effort with Mirante returning the favour from Jose Callejon's 25-yard shot and Marek Hamsik's attempt.
Napoli then thought they had gone ahead after 73 minutes when Higuain headed home a corner but he was adjudged to have been in an offside position.
Napoli's frustration at this was exacerbated eight minutes later when Parma scored what proved to be the winner.
It was a fine goal by Cassano, who skirted the Napoli box before slotting home at the far post with a precise right-footed shot.
Napoli came within inches of levelling with just a minute left but Dries Martens' free-kick skimmed the bar and instead it was Parma who claimed a shock victory.