DaMarcus Beasley's late strike earned Manchester City an unlikely win that keeps West Ham in the bottom three.
Hammers keeper Robert Green had been a virtual spectator for most of the game but was helpless as substitute Beasley ran past two defenders and fired home.
Teddy Sheringham had gone close with a deflected effort for the home side but, for all their possession, the Hammers created little in front of goal.
City had to survive some concerted late pressure but left with the points.
Following on from their Boxing Day triumph over Sheffield United, it was the first time Stuart Pearce's side had managed back-to-back victories for 15 months.
And while Hammers boss Alan Curbishley may have seen his side beat Manchester United in his first game in charge, a failure to win any of their three matches since has kept his side at the wrong end of the table.
606: DEBATE
Both teams have had difficult seasons and Pearce's approach here suggested he saw one point as a decent return, let alone three.
The onus was on West Ham to break the Blues down but only veteran striker Sheringham looked the part in front of goal, although Marlon Harewood's physical presence made life difficult for City's defence.
It was Sheringham who went closest to breaking the deadlock before half-time, seeing one shot deflected just wide after Sylvain Distin's mistake let Harewood in.
The game did not improve as a spectacle after the break and there was little in the way of quality from either side.
Sheringham saw a free-kick fly wide and Hayden Mullins and Carlos Tevez also went close but City keeper Nicky Weaver was not called into action.
Green was even less involved at the other end but he was finally forced to make a save from the impressive Vassell with 15 minutes left.
And with the introduction of Georgious Samaras and Beasley from the bench, City at last began to threaten.
There still appeared to be little danger when Beasley picked the ball up outside the area but he made for goal and ghosted past Anton Ferdinand and Danny Gabbidon before smashing his shot past Green.
It was a barely deserved winner for City but Pearce will hope his side can build on their festive form in the second half of the season - while Curbishley has only a relegation struggle to look forward to.
West Ham manager Alan Curbishley:
"Everybody has been telling me how good the players are but the Premiership is unforgiving. They played well last season but this is a different year.
"Anybody in our position would be looking to bring in a goalscorer but will clubs be letting them go?"
Manchester City manager Stuart Pearce on his side's second away win in five days:
"It was a scrappy game but I thought we showed a lot of spirit.
"It has been difficult for DaMarcus since he joined as he picked up an injury. He could easily have got depressed but he was always smiling."
West Ham: Green, Dailly, Ferdinand, Gabbidon (Mears 86), Spector, Benayoun, Bowyer, Mullins, Etherington (Tevez 56), Sheringham (Cole 68), Harewood.
Subs Not Used: Carroll, Noble.
Booked: Spector.
Man City: Weaver, Onuoha, Dunne, Distin, Jordan, Trabelsi, Ireland (Beasley 65), Dabo, Richards, Vassell (Miller 88), Corradi (Samaras 70).
Subs Not Used: Isaksson, Thatcher.
Booked: Vassell, Jordan.
Goals: Beasley 83.
Att: 34,574
Ref: S Bennett (Kent).