The Hammers had not beaten the Seagulls since their promotion to the Premier League – a run that spanned six years and 12 games.
However, goals from James Ward-Prowse – his first for the Irons and 50th in the Premier League – Jarrod Bowen and Michail Antonio secured a fine victory for David Moyes’ side.
Alphonse Areola was in inspired form for the Hammers but was finally beaten when Pascal Gross found the corner with an inch perfect strike from outside the box, with ten minutes remaining.
Evan Ferguson and Lewis Dunk went close in injury-time but it was too little, too late for Albion, who were a shadow of the side that dismantled Wolves and Luton.
Here’s how Roberto De Zerbi’s players rated:
. Brighton 1-3 West Ham
West Ham put on a counter attacking masterclass as they recorded their first ever Premier League victory over a below-par Brighton. Photo: Henry Browne/Getty Images
. Bart Verbruggen - 5
Not the way he would have wanted his first Premier League game to go. Made a few comfortable saves but couldn't stop any of the goals. In fairness, he wasn't really helped by his defenders Photo: Charlie Crowhurst/Getty Images
. James Milner - 5
Looked a bit leggy in the first half and struggled to keep up with West Ham's pacey attackers. Involved in a heated exchange, showing he's still got that fire in his belly. Looking to make an impact going forward. Good effort saved as Albion looked to fight back from three goal down Photo: Charlie Crowhurst/Getty Images
. Lewis Dunk - 6
Not his best game for Brighton but was among the better performers on the pitch. Was too casual in certain moments. Two cracking headers kept out by an inspired Alphonse Areola and another cleared off the line by a defender. Photo: Henry Browne/Getty Images
. Adam Webster - 3
Webster won't look back at this game with any fondness. He was at fault for the first goal after being bullied off the ball by Antonio. He wanted a foul but it was never going to be given. Gave Benrahma far too much time and space to find a cross for the second goal, finished off by Bowen. The defender was beaten again by Antonio for the third goal. Not a good day at the office for the defender Photo: Henry Browne/Getty Images
1. West Ham 1-1 Brighton
Brighton let a lead slip once again as their Premier League winless run extended to five games with a draw at West Ham. (Photo by Alex Broadway/Getty Images) Photo: Alex Broadway/Getty Images
2. Bart Verbruggen - 6
Saved from Bowen after seven minutes from a tight angle. Save from Bowen initially but Kudus scored the rebound. The keeper arguably could have pushed it away from the danger zone. Diving save at 1-1. Photo: Charlie Crowhurst/Getty Images
3. Joel Veltman - 6
Great to see him back in action. Good sliding challenge on fellow former Ajax man Kudus – before he was later booked for pulling down the West Ham star. Replaced by Lamptey as the Dutchman’s minutes are managed – and to be cautious of avoiding a red card. Photo: Alex Broadway/Getty Images
4. Jan Paul van Hecke - 6
Treated for head injury after getting a kick by Mavropanos. Was able to carry on with his bandaged up. Good news for Brighton who desperately need the Dutchman to stay fit. Header forward was intercepted and it led to the equaliser. Dunk saved Van Hecke after he was caught in possession at 1-1. Nice pass to Minteh who nearly scored. Photo: Alex Broadway/Getty Images