Jose Callejon scored the only goal of the game nine minutes from time as Rafa Benitez's men strengthened their claim for Champions League football against next season.
The result will also have been met with delight in Turin, where Juventus now hold a 14-point advantage over Roma, who have a game in hand, with a third straight Scudetto looking increasingly likely.
It was a game which swung from end to end with both goalkeepers called into action regularly, and rising to the challenges thrown their way.
Medhi Benatia had the ball in the back of the net in the 26th minute, but the goal was ruled out for offside.
It was nevertheless a warning with Roma putting Napoli under some heavy pressure in the first half, Gervinho looking particularly lively and he brought the first great save out of Pepe Reina in the 28th minute.
Two minutes later, the former Arsenal player exchanged passes with Alessandro Florenzi, but was unable to control the return ball with only Reina to beat.
Just before half time, Michel Bastos had Reina at full stretch to turn his angled shot over before Morgan De Sanctis was called into action for the first time on the stroke of half-time to turn Dries Mertens' shot away.
Callejon squandered a great chance to put the hosts in front early in the second half with only De Sanctis to beat, but the Roma goalkeeper blocked with his legs.
The ball was not fully cleared, however, and a cross from Christian Maggio was sent over the crossbar on the half-volley by Gonzalo Higuain.
Napoli were now starting to ask more of the questions.
Reina still had to be alert to turn a deflected Maicon shot behind with a strong left hand before Callejon's 20-yard volley was diffused by De Sanctis.
There was no way any goalkeeper was going to get near to Callejon's next effort, though, as he planted Faouzi Ghoulam's cross better than a postage stamp in the top right-hand corner, the ball grazing both the post and the crossbar on its way in.
The game became stretched for the final nine minutes as Roma searched for an equaliser, but they could not find one as their berth in the Champions League group stage came under pressure, and their Scudetto hopes suffered a further setback.