Andrea Stramaccioni's side struck twice in the first-half to ensure they leapfrogged the Partenopei to within four points of the league leaders
Fredy Guarin gave the hosts an early lead and Diego Milito doubled their advantage five minutes before the break, while Edinson Cavani pulled one back for the visitors.
With both teams playing variations of 3-5-2, the game was always likely to be decided somewhere within the packed midfield. Both sides prefer to play on the counter and it was end-to-end from the outset, with both preferring to attack in quick transitions rather than via any sustained spell of possession.
Wesley Sneijder was officially missing the game because of a calf injury, so Guarin was charged with relieving some of the creative burden from Inter’s Antonio Cassano.
While the Colombian’s decision making can often let him down, his ability to strike the ball from distance mean he always poses a significant goal threat – and it was he who put the hosts ahead inside eight minutes.
Cassano arrowed in a deep corner that that sailed over the challenging pack to find the onrushing Guarin, who hammered his controlled volley inside Morgan De Sanctis’ near post from just inside the area.
Lorenzo Insigne almost had the Partenopei level 10 minutes later, leading a swift counterattack with Cavani before cutting inside and bending his shot inches wide of the far post.
Between them, Cavani and Marek Hamsik had earned 25 of Napoli’s 33 points so far this season and they combined for the first time when Hamsik dragged his shot wide from the edge of the box after some fine approach play from the Uruguayan.
Cavani himself then went close, wasting his side’s best chance of the first half shortly before the half-hour mark. The 25-year-old found himself all lone at the back post to meet Inigne’s floated cross, but the usually deadly striker sent his header bouncing wide from just six yards.
While Napoli looked to be taking control of the game, Milito struck to double Inter’s lead five minutes before the break. Guarin repaid his coach’s faith slotting a short pass for the Argentine to place his finish inside the far post from 12 yards. Having got a full hand to the ball, De Sanctis will be disappointed not to have deflected effort away.
Desperate to get his side back into the game, Walter Mazzarri switched his side’s tact at half-time, introducing Goran Pandev for Alessandro Gamberini at half-time after Insigne and Cavani looked slightly isolated up front.
The switch left Napoli man-to-man at the back as Cassano took his position further forward, and the Italy international nearly made it three when he peeled off his marker to collect Alvaro Perriera’s pass and smash his low shot against the near post from close range.
Pandev’s introduction created more space for those breaking from midfield, and he made an immediate impact on 53 minutes, shortly after Samir Handanovic had made a flying save to deny Gokhan Inler. Cavani pounced to grab his 11th league goal of the season, driving in from close range following a chaotic scramble that had seen Pandev strike the bar inside the six-yard box.
Insigne then went close as Napoli poured forward, his dragged shot almost evading a sprawling Handanovic to find an unmarked Cavani for a tap in, but the Inter keeper did well to smother the ball.
Hearts were once again in Nerazzurri mouths when Christian Maggio headed straight at Handanovic three minutes before the end, and also when Cavani saw his fierce shot from 12 yards well blocked.
But try as Napoli did, they could not find an equaliser as Inter held out for their fifth victory in their last six home games, and one that will no doubt cement their label as real title contenders.