Match ends, Brighton and Hove Albion 1, Fulham 2.
Darren Bent struck a debut goal for Brighton, but they squandered the lead as Fulham climbed to 16th in the table with victory at the Amex Stadium.
Striker Bent, who joined the Seagulls on loan this week, broke the deadlock on 52 minutes with a first-time finish after Adrian Colunga picked him out.
But Lasse Vigen Christensen created Hugo Rodallega's powerful leveller before netting a deflected winner.
Colunga was sent off late on as Brighton fell into the bottom three.
Sami Hyypia's side have now won just once in their past 12 matches and face a trip to Championship leaders Derby County next week.
The Seagulls have found goals hard to come by, and the fact defender Lewis Dunk is their top-scorer underlined the need for Bent's arrival.
The 30-year-old brings international pedigree and a point to prove to parent club Aston Villa, not to mention more than 150 league goals.
But he was denied in the opening period as Fulham keeper Marcus Bettinelli saved a header with his legs.
The Cottagers, where Bent spent a spell on loan last season, also threatened through Rodallega - but he wasted a chance moments before the home side took the lead.
Bent drove the ball between Bettinelli's legs to give his new side the lead, but Fulham responded when Rodallega clinically beat former team-mate David Stockdale from 10 yards.
Bryan Ruiz went close with a header for the visitors before passing for Christensen to net his fourth goal of the season with a deflected strike.
Colunga was shown a second yellow card in added time for a foul on Scott Parker, and Fulham saw out the game to secure a sixth victory in 11 games.
Brighton manager Sami Hyypia:
"We need to turn it around very quickly. It is a very tight league and if you win a few games you'll be in mid-table.
"It's not a nice position to be in and the fans have a right to be unhappy. We must try to make everything better.
"We can affect what we do on the training field and we are working hard to correct it.
"Everyone has to toughen up and be more concentrated."
Fulham manager Kit Symons:
"We will keep trying to improve on every aspect of the game. We want to get up in a decent place and are certainly going in the right direction.
"In this league you're never out of a relegation battle until you're safe and the players must not be complacent.
"You can get sucked into a scrap and I've seen both sides of it.
"The boys showed real good character after we didn't start well. We weren't clinical enough but our two strikers were excellent in the second half."
- 32BennettSubstituted forMarchat 78'minutes
- 7ColungaBooked at 90mins
- 25Lua LuaSubstituted forInceat 23'minutesBooked at 72mins
- 37GrimmerBooked at 45minsSubstituted forZveroticat 85'minutes
- 8ParkerBooked at 65mins
- 28HyndmanSubstituted forFofanaat 63'minutes
- 10RuizSubstituted forWoodrowat 80'minutes
- 44McCormackBooked at 81mins
- Simon Hooper
- Shots on Target
Second Half ends, Brighton and Hove Albion 1, Fulham 2.
Offside, Brighton and Hove Albion. Solly March tries a through ball, but Lewis Dunk is caught offside.
Foul by Solly March (Brighton and Hove Albion).
Ross McCormack (Fulham) wins a free kick on the left wing.
Second yellow card to Adrián Colunga (Brighton and Hove Albion) for a bad foul.
Foul by Adrián Colunga (Brighton and Hove Albion).
Scott Parker (Fulham) wins a free kick in the defensive half.
Attempt blocked. Solly March (Brighton and Hove Albion) left footed shot from outside the box is blocked.
Attempt missed. Solly March (Brighton and Hove Albion) left footed shot from outside the box is too high from a direct free kick.
Adrián Colunga (Brighton and Hove Albion) is shown the yellow card.
Darren Bent (Brighton and Hove Albion) wins a free kick in the attacking half.
Foul by Scott Parker (Fulham).
Offside, Fulham. Lasse Vigen Christensen tries a through ball, but Cauley Woodrow is caught offside.
Attempt missed. Jake Forster-Caskey (Brighton and Hove Albion) left footed shot from outside the box is too high.
Substitution, Fulham. Elsad Zverotic replaces Jack Grimmer.
Foul by Cauley Woodrow (Fulham).
Solly March (Brighton and Hove Albion) wins a free kick on the left wing.
Ross McCormack (Fulham) is shown the yellow card.
Substitution, Fulham. Cauley Woodrow replaces Bryan Ruiz because of an injury.