A 48th-minute strike by Declan Rice threw Arsenal’s top four bid into further doubt with the point difference between the Gunners and 4th placed Chelsea increasing to six.
Rice fired home a pass from Samir Nasri to hand Arsenal their 5th defeat of the 2018/2019 Premier League campaign.
Alex Iwobi lasted the entire duration of the game but failed to make any meaningful impact as the Gunners suffered their first away defeat to West Ham since 2006.
Iwobi who had scored in Arsenal’s last two matches had an opportunity in the 10th minute to shoot Arsenal lead but his feeble shot was saved by West Ham goalie Lukasz Fabianski.
The victory moved West Ham to 8th on the league log with Arsenal stuck on 5th position with 41 points.
The game was Iwobi’s 18th of the season with only two goals to show for.