Brentford produced an excellent team performance to inflict Brighton's first defeat at the Amex since January 1 2016.
Scott Hogan scored a goal in each half to give the Bees the three points but it was built off the back of an excellent defensive performance in the first half.
After being under the cosh for the bulk of the first 30 minutes, Lewis Macleod sent the Bees striker clear and he slid the ball past David Stockdale, who punched the turf in frustration.
The Bees were stronger in the second period and Harlee Dean teed the striker up for his second as he blasted home, over the Seagulls goalkeeper, into the roof of the net.
After a strong first five minutes from the Bees, Brighton started to dominate possession and territory and the back four of Maxime Colin, Dean, John Egan and Callum Elder all produced strong displays to prevent the Seagulls having any meaningful opportunities.
When called up, Dan Bentley in the Brentford goal was on hand to mop up any danger.
The Bees were happy to play on the counter and Hogan tested the offside trap on a number of occasions.
When he did beat the trap, he made no mistake as he slotted the ball past Stockdale at his near post to give the visitors the lead after 29 minutes.
Dean and Egan combined brilliantly to preserve that lead before the break to clear the ball off the line from Tomer Hemed's header, while Ryan Woods mopped everything up in front of the back four alongside Nico Yennaris.
That defence had to change at the break as Elder was forced off with Andreas Bjelland coming on in his place.
The Bees made a stronger start to the second half as Brighton opened up in pursuit of an equaliser.
Hogan had a couple of opportunities to add a second before Bjelland had a looping header cleared off the line.
Brentford did double their advantage and it came about from superb work from Dean, harrying the Brighton defence before putting the ball in for Hogan who made no mistake from a tight angle.
The Bees were able to see out the remaining 19 minutes, with Hogan nearly completing his hat-trick, to take the three points.