The former Real Madrid man scored the winner as Rafa Benitez's troops moved to within three points of Rudi Garcia's side in the Serie A table
Both sides created a number of chances throughout the game, but Jose Callejon's header late in the second half eventually made the difference for the hosts and cut the gap to the second-placed Giallorossi in the table.
The away side got the first good chance of the game as Gervinho threatened after just three minutes of play, but the Cote d'Ivoire star failed to find the net from inside the area.
Roma were then dealt a big blow when Kevin Strootman was forced off with a knee injury and Napoli briefly took over the initiative.
Nevertheless, the guests looked to have grabbed the lead halfway through the first half when Mehdi Benatia headed home from close range, only to see the referee disallow the goal for offside.
Gervinho continued to cause the Napoli defence all kinds of trouble with his silky dribbles and the former Arsenal man should have opened the scoring in the 37th minute, but Pepe Reina pulled off a fine safe to deny the attacker.
The home team struggled to create any chances of note, yet went close in the dying minutes of the first half via Dries Mertens, whose shot was eventually parried by Morgan De Sanctis.
Napoli did start the second half the better and once more Mertens tried his luck, but the Belgium international's attempt from outside the area only grazed the crossbar.
Rafa Benitez's men again threatened shortly after through Callejon, who found himself one-on-one with De Sanctis, but the Roma goalkeeper denied the former Madrid attacker with his right foot.
A Maicon cross from the right then nearly saw Roma go ahead, but Reina pulled off a superb reflex stop to keep the ball out, while Alessandro Florenzi headed inches wide after good work from the Brazilian in the 75th minute.
Napoli broke the deadlock at last with 10 minutes to go after some good work from Faouzi Ghoulam. The left-back found Callejon with a perfect cross and the versatile attacker beat De Sanctis with a powerful header that went in off the crossbar to make it 1-0.
Napoli remain third in Serie A with 55 points from 27 games. Their next match is the Europa League clash with Porto on Thursday.
Roma are still sitting second in the table, trailing leaders Juventus by 14 points, but with a game in hand. They resume Serie A action at home against Udinese on March 17.