Arsenal gain first away win under interim manager Freddie Ljungberg as the Gunner came from a goal down to beat West Ham to end winless run of nine matches.
The Gunners had not won since a 3-2 success over Portuguese side Vitoria de Guimaraes in the Europa League on 24 October and sacked Unai Emery last month.
Former Arsenal midfielder Ljungberg, in temporary charge in his first managerial role, had seen his team draw 2-2 at Norwich and lose 2-1 at home against Brighton on Thursday.
The Gunners failed to have a shot on target in the opening hour before three goals in nine minutes turned the match around at London Stadium.
This result also increases the pressure on West Ham boss Manuel Pellegrini, with the Hammers 16th, only one point above the bottom three, and with only one win in 11 matches.Arsenal jumped up from 11th to ninth, seven points behind fourth-placed Chelsea but 24 adrift of Premier League leaders Liverpool.
The only negatives for the Gunners were three injuries as right-back Hector Bellerin was hurt in the warm-up, left-back Kieran Tierney went off with a shoulder problem and midfielder Granit Xhaka went off late on with a head injury.