Naif Aguird Scored from a set piece in the first half to give the London side breathing room in the relegation battle.
The win lifted West Ham to 14th (27 points) in the league standings.
The teams were ranked 19th and 20th on the table before kickoff. Southampton remained bottom, three points from the safety zone.
West Ham took the lead in the 25th minute when Aguired headed home a free kick but they had an agonizing wait as VAR took several minutes to check whether the Moroccan defender was offside before awarding the goal.
The away team had more possession but the goal lit a spark at West Ham and Jarrod Bowen almost doubled the lead on the counter-attack before half-time when his shot beat the keeper but came off the crossbar.
At the other end, Lukasz Fabianski was tested several times by Southampton but the Polish goalkeeper was up to the task, making cool saves to keep a clean sheet, although Nigerian forward Paul Onuchu’s late header hit his crossbar. .
Southampton lacked creativity in attack, however, as West Ham – who have a game in hand over their relegation rivals – moved up five places and provided welcome relief for their manager David Moyes.
(with inputs from Reuters)