Danny Welbeck opened the scoring for Albion in the 84th minute before Said Benrahma netted for the Hammers just three minutes later.
The result leaves a serious dent in the Hammers’ hopes of securing Champions League qualification this season, but manager David Moyes still found time to praise the Seagulls in his post-match press conference.
He said: "I thought we played very well for long periods in the game, especially in the first-half.
"I felt Brighton improved in the second-half.
"We didn't do enough in the final third. Our decision making was poor and there was not enough quality in the pass.
"We gave away a really bad goal. We can't keep giving the opposition a goal.
"We've had games where we've gone three or four up and tonight could have been another one if we had clinical finishing.
"All credit to Brighton. I think they are a good side."
Next up for Brighton is a clash against newly-crowned champions Manchester City at the Amex Stadium.
For the first time in months, Albion will be able to welcome a limited number of supporters back to the ground after the government eased Coronavirus restrictions on Monday.
The Seagulls were beaten 1-0 when the two sides last played each other in the league, with Phil Foden bagging the vital goal.
We’ve gathered the best of today’s Premier League transfer speculation below...
1. PSG after Salah
PSG have already been in touch with Mo Salah’s camp, presumably trying to find out whether the Liverpool player would be interested in a move to France. (L'Equipe) (Photo by Laurence Griffiths/Getty Images) Photo: Laurence Griffiths
2. BERLIN, GERMANY - MAY 13: Jadon Sancho of Borussia Dortmund celebrates with the trophy after winning the DFB Cup final match between RB Leipzig and Borussia Dortmund at Olympic Stadium on May 13, 2021 in Berlin, Germany. Sporting stadiums around Germany remain under strict restrictions due to the Coronavirus Pandemic as Government social distancing laws prohibit fans inside venues resulting in games being played behind closed doors. (Photo by Martin Rose/Getty Images)
Manchester United are in pole position for signing Jadon Sancho and the talks between the Red Devils and the Borussia Dortmund star’s agent are already underway. (Sport1) (Photo by Martin Rose/Getty Images) Photo: Martin Rose
3. Burnley and Brighton to battle for Man United player
Sunderland have made an offer to Manchester United youngster Jacob Carney with Brighton and Burnley also in the running. (The Sun) (Photo by Catherine Ivill/Getty Images) Photo: Catherine Ivill
4. Brighton told to sign Toney
Former Crystal Palace striker Clinton Morrison has claimed Brighton should sign Brentford hitman Ivan Toney to push them on to the next level. (Sky Sports) (Photo by Justin Setterfield/Getty Images) Photo: Justin Setterfield