The hosts started positively and looked to play the ball behind Pep Guardiola’s backline, but they found themselves behind just nine minutes into proceedings.
After a scramble for possession in Man City’s half, Erling Haaland popped the ball off to Tijjani Reijnders and flew up the pitch to get it back, before beating David Raya for an 11th goal in six matches for club and country.
While Arsenal came forward as they looked to recover, the Citizens stood firm defensively and continued to carry a threat, with Reijnders seeing his shot saved by Raya.
The visitors’ approach was largely pragmatic, though, as they took their time getting the ball back into play – much to the frustration of the Emirates’ home support – and often ensured they dealt with Arsenal’s set-pieces.
There was still a warning when Gianluigi Donnarumma’s punch on a Declan Rice corner was unconvincing as William Saliba headed over.
In open play, meanwhile, Riccardo Calafiori sent an attempt over and Noni Madueke’s venomous strike was saved as the Gunners showed plenty of intent before the break.
Mikel Arteta went for it straight from the restart by bringing on Bukayo Saka and Eberechi Eze, and a cross from the former saw the ball fall to Martin Zubimendi for a chance that he sent marginally over the crossbar.
Both substitutes had also hit a shot inside seven second-half minutes, but there was a scare at the other end as Haaland’s shot was saved by Raya and Eze’s attempted clearance hit Rice but bounced over the crossbar.
Leandro Trossard was then denied as Arsenal continued to assert themselves so much that Guardiola resorted to bringing Phil Foden and Haaland off for Nathan Ake and Nico González.
Much of the late play was essentially attack against defence, but the defence won time after time, with Calafiori heading over and hitting a speculative shot off target.
On the one occasion it didn’t, Martinelli punished the Citizens by latching onto Eze’s ball behind and dinking his effort over Donnarumma to inspire rapturous celebrations in the Etihad Stadium, with the goal keeping the second-placed Gunners three points ahead of Man City.
While it may not be a defeat for the Citizens, it will undoubtedly be a significantly disappointing blow after they had come so close to victory.
Flashscore Man of the Match: Tijjani Reijnders (Manchester City)