Former Rangers star Gennaro Gattuso suffered a disappointing debut as new Napoli boss.
Gervinho's stoppage-time goal earned Parma a 2-1 win at the Stadio San Paolo to extend the home side's winless run in Serie A to eight games.
Dejan Kulusevski's early opener was cancelled out by an Arkadiusz Milik header midway through the second half, but ex- Arsenal forward Gervinho finished off a clinical counter-attack to earn a late victory.
Former AC Milan manager Gattuso, a favourite at Rangers during the late 1990s, was brought in to replace the sacked Carlo Ancelotti last week.
A poor start to the season left Napoli in seventh place and on their worst run of league form in 19 years.
And the defeat by Parma means Napoli have failed to win four consecutive Serie A home games for the first time since March 2010.
The result sees Parma move above Gattuso's side into seventh place on 24 points, leaving Napoli eighth on 21 and at risk of sliding further down the table before the end of the weekend.
