Arsenal started with Eddie Nketiah as a lone striker but his second-half replacement Alexandre Lacazette scored the winner against West Ham.
The France international scored only his second league goal of 2020, converting from close range in the 78th minute to clinch three points for Mikel Arteta's side, who struggled to break down a battling West Ham team before Lacazette's second-half introduction.
The best chances of the afternoon before the goal fell to Hammers striker Michail Antonio, who misfired from close range either side of half-time, and Hammers boss David Moyes will be disappointed his side failed to hang on for a precious point towards their battle against relegation.
Arteta started with Eddie Nketiah as a lone striker and failed to capitalise on what little possession came his way, while Gunners top scorer Pierre-Emerick Aubameyang had an uncharacteristically quiet afternoon as he chased his 50th Premier League goal.
The result means Moyes is still without a win in 16 top-flight away games against Arsenal – no manager in Premier League history has taken charge of more winless away games against a single opponent.
Premier League Standings
Match Events
11' MISS! Antonio misses a golden chance
BIG CHANCE! Antonio is played in down the right. He has just Leno to beat but decides to square to Haller alongside him, only to play the pass behind his team-mate.
13' CLOSE! Ozil and Nketiah's shot denied
Ogbonna can only half-clear a cross and Ozil has a chance to shoot from 10 yards. The ball is heading for the target but Diop puts his body in the way to block it.
22' CROSSBAR! Sokratis nearly scores for Arsenal
Ceballos' teasing cross from the right is flicked on by the head of Ngakia before Aubameyang can get on the end of it. The corner is not properly dealt with by West Ham and Sokratis turns Aubameyang's cross onto the crossbar with his head.
41' AGAIN! Antonio misses a good chance
WHAT A SITTER! Diop heads down a corner and Antonio somehow fires wide on the turn from no more than four yards out. He has to score!
56' SAVE! Fine stop from Leno
Haller flicks on Cresswell's left-sided cross and Antonio adjusts his body in time to get away a shot. Leno reacts brilliantly to make a point-blank save.
78' GOAL! Arsenal 1-0 West Ham (Lacazette)
GOAL GIVEN BY VAR!!! Lacazette's goal was initially ruled out for offside, but a VAR check shows the striker was just about the right side of Ogbonna when volleying Ozil's cushioned pass beyond Fabianski.
83' AGAIN! What a save from Leno
Bowen plays a cute little pass in behind and Haller, having got away from David Luiz, slides in to test Leno with a first-time shot from five yards out. That has to go down as a decent opportunity for West Ham.