West Brom score three in the first half
West Brom started the game off well, with James McClean going close in the first minute but his shot was beaten away by Adrian.
In the eighth minute, West Brom got a well-deserved opening goal when Artur Masuaku handled curiously in the area. Nacer Chadli converted the penalty with ease after sending the goalkeeper the wrong way to give the home team a 1-0 lead.
West Ham then built up a head of steam themselves, with Manuel Lanzini beating Claudio Yacob with some clever skill 20 yards out and firing a rasping drive just past the post. Ben Foster may have been beaten that time but the Baggies' stopper had to be on top form to deny Michail Antonio when one-on-one.
Almost immediately afterwards, the home side grabbed their second of the game. Angelo Ogbonna's horrid clearance fell at the feet of Chadli, who slid the ball over to Salomon Rondon. The Venezuelan striker didn't need a second invitation to shoot, and buried the ball low into the far corner past Adrian's despairing dive.
Just seven minutes later and, crucially, minutes before the break, West Brom got their third. The Hammers made a mess of clearing a corner, and the ball fell sweetly for Chadli to smash at goal from the penalty spot. His effort was screaming wide until McClean got the key touch to delfect the ball in
Second half improves for West Ham, but West Brom manage to escape
Whatever Slaven Bilic said at the break certainly worked, as the East London outfit came back firing to get a foothold in the game. After Jonathan Calleri's shot was well-blocked by the home defence, Antonio's powerful shot had to be gathered at the second attempt by Foster.
Then, once more, West Ham were hit with a sucker punch. After throwing everything forward for a corner, Darren Fletcher managed to slide Rondon through on goal from the half-way line with a beautiful ball. One-on-one with Adrian, the forward opted for the simple option and returned the favour for Chadli to complete his brace.
From there, the fightback was mounted. After Dmitri Payet had rattled the joint with an oh-so sweetly struck free-kick, the Frenchman then picked up a corner on the far side and sent in a superb delivery to meet the oncoming Antonio. The winger bulleted a trademark header past Foster to reduce the deficit.
The nerves soon kicked in just four minutes later when Payet, now in his groove, danced his way into the West Brom box before being hauled down. Mark Clattenburg had no hesitation in pointing to the spot, and Lanzini squeezed the penalty under Foster's arm to make it four-two.
James Collins was then denied by Foster, who beat away his close-range effort. However, it would turn out to be West Brom's day, as they managed to hold on for a much-needed win. West Ham face Sunderland in their next Premier League match, while West Brom travel to Stoke City.
Rondon has scored a goal in four of his last seven Premier League matches, while Chadli's penalty was the first he had even taken in the Premier League.
West Ham have conceded at least two goals in 12 of their last 15 Premier League matches.
West Brom manager Tony Pulis said: "It was a good peformance. We played well at Bournemouth last week and probbably created many opportunities. The difference is we've won the game and that chances people's perceptions."
Meanwhile, West Ham's Slaven Bilic explained: "They (West Brom) deserved it. I felt embarrassed at half-time. We were three down and we can say that some of the goals were individual mistakes."