Napoli never recovered from a disastrous opening 15 minutes, as they were beaten 2-0 by Arsenal in London.
Elsewhere in the group, Borussia Dortmund swept Olympique Marseille aside 3-0.
Both sides won their opening games, so this was a head-to-head for the top of Champions League Group F. Gonzalo Higuain was looking forward to facing the club he nearly joined this summer, but failed a fitness test for a thigh problem and watched from the stands. Arsene Wenger picked Mikel Arteta and Tomas Rosicky along with new signing Mesut Ozil and ex-Milan midfielder Mathieu Flamini, but had to do without the injured Theo Walcott, Santi Cazorla, Alex Oxlade-Chamberlain, Abou Diaby, Lukas Podolski and Yaya Sanogo.
While Rafa Benitez had never won here in the Premier League, he was unbeaten in four Champions League away games against the Gunners.
Arsenal went in front with their first chance, as Aaron Ramsey burst down the right and pulled back for Mesut Ozil’s powerful finish from the edge of the box. It was the ex-Real Madrid man’s first goal in an Arsenal jersey.
Napoli seemed to not really be out of the locker room yet, as they conceded a similar second. This time Ozil was the provider, getting down that same right flank after a defensive error to pull back for Olivier Giroud’s tap-in from five yards.
It took 20 minutes for the Partenopei to enter the fray, as Miguel Angel Britos turned a free header off target from Lorenzo Insigne’s corner and Jose Maria Callejon’s free kick was over. However, they remained shambolic in defence with Giandomenico Mesto particularly slow to react on Ramsey, so was fortunate Raul Albiol blocked in the box.
Albiol charged down another attempt from Flamini after Marek Hamsik had lost control during a promising run.
Within 49 seconds of the restart Giroud had again gone clear in acres of space down the right, but Rosicky didn’t connect with the ball from six yards. Gokhan Inler and Callejon tried from distance, while Wojciech Szczesny did well to pluck a corner off the head of Britos.
Rafa Benitez made a change on the hour mark, introducing Dries Mertens for Pandev, so Callejon became the centre-forward. A Mertens curling effort from distance was plucked out from under the bar by Szczesny, but Pepe Reina needed a considerably tougher save to deny Laurent Koscielny from close range after Arteta knocked down an Ozil cross.
Duvan Zapata made his Champions League debut, but Napoli were simply never in the game at the Emirates.
Arsenal 2-0 Napoli
Scorers: Ozil 8 (A), Giroud 15 (A)
Arsenal: Szczesny; Sagna, Mertesacker, Koscielny, Gibbs; Flamini, Arteta; Ramsey (Monreal 88), Ozil, Rosicky (Wilshere 63); Giroud
Napoli: Reina; Mesto, Albiol (Fernandez 83), Britos, Zuniga; Inler, Behrami; Callejon (Duvan 77), Hamsik, Insigne; Pandev (Mertens 60)
Ref: Mazic (SRB)