AFC Bournemouth were triumphant in a seven-goal thriller at Upton Park.
A Callum Wilson hat-trick and a single goal from substitute Marc Pugh secured the Cherries their first Barclays Premier League points of the season.
It was the home side that had the ball in the net first, though. Winston Reid powered an out-swinging corner past Artur Boruc in the opening minutes, but referee Jonathan Moss ruled the header out for a foul on Tommy Elphick.
The Cherries responded quickly and a dangerous Matt Ritchie free-kick soon caused trouble. Crossing in deep from the right, the Scotland international found a gap between the defence and Darren Randolph in the West Ham goal, but neither Steve Cook nor Elphick could capitalize on the loose ball.
AFC Bournemouth then got their breakthrough soon after. Relentless work from Simon Francis saw him dispossess Aaron Creswell on the West Ham byline, and the defender then drilled the ball into the near post where Callum Wilson arrived to fire the Cherries ahead.
Creswell almost redeemed himself straight after as he nutmegged Max Gradel and delivered into the Cherries box, but Cheikhou Kouyate was unable to direct his back-post header downwards.
Eddie Howe’s men really began to take a hold of the encounter from here on in, and they soon doubled their lead. A prolonged spell of possession around the home side’s penalty area led to Cresswell gifting a loose pass to Wilson, and last term's leading scorer made no mistake from close range.
With a two-goal advantage the Cherries looked in complete control. Francis picked up the ball deep inside the West Ham half and drilled a cross in to the penalty area once more, but Joshua King was unable to control his first-time shot and it flew over from close range.
Gradel was next with a chance for AFC Bournemouth. Wilson bore down on goal and squared the ball into the path of the on-rushing Ivorian, but he was denied by Randolph who pushed the ball behind for a corner just before the break.
The home side started the second half well and soon pegged one back. A looping ball was punched clear by Boruc in the Cherries goal, but Mark Noble was felled from the rebound and awarded a penalty. The West Ham captain then brushed himself down and duly converted from the spot.
Sensing their opportunity, West Ham continued to commit forward and soon had their equaliser. Kouyate was the first to react as Boruc palmed away his shot, and the Senegal international rocketed the loose ball into roof of the net to level proceedings.
The Cherries then tried to find their rhythm again and almost came close when an ambitious 30-yard strike from Gradel whizzed past West Ham’s post.
But it was substitute Marc Pugh that was to make the real difference. Finding space on the left of the penalty area he exhibited the coolest of heads to cut back past a sliding tackle and tuck the ball into Randolph’s far corner to restore the lead.
The visitors then extended their lead once more. Tireless work from Gradel allowed the summer signing to steal the ball from Carl Jenkinson and burst into the West Ham penalty where the defender retaliated and brought him down.
Referee Moss was then forced to point to the spot for the second time in the game and he dismissed Jenkinson before Wilson stepped up and converted to seal his Premier League hat-trick.
West Ham refused to rollover, though, and two minutes later they had the ball in the net once more. Substitute Modibo Maiga burst through the Cherries defence and calmly sent Boruc the wrong way to rescue a lifeline for the home side.
But a resolute defensive display, including a hack off of the line in the dying moments, saw the Cherries take all three points back to Vitality Stadium.
Cherries: Boruc, Francis, Elphick (c), Cook, Daniels, Ritchie (Smith, 90), O'Kane, Surman, Gradel (Gosling, 85), King (Pugh, 50), Wilson.
Not used: Federici, Distin, Mings, Kermorgant.