Inigo Calderon made an impressive return from injury with a hand in both of Albion's goals, which were scored by Ashley Barnes in the second minute and Andrea Orlandi after 25.
Derby manager Nigel Clough, who this week celebrated four years in the job, saw his side create very little as the Rams slipped to an eighth away league loss of the season.
Jeff Hendrick did pull a goal back midway through the second half but the Rams never really looked like rescuing anything from the game.
Brighton boss Gus Poyet made three changes to the side that started the FA Cup win over Newcastle last weekend.
Tomasz Kuszczak replaced Casper Ankergren in goal while Calderon returned at right-back following a knee problem, so David Lopez moved back into midfield with Gary Dicker dropping to the bench.
Leading scorer Craig Mackail-Smith missed out due to a hamstring injury but Will Buckley was fit to return to the side.
Less than 80 seconds were on the clock when Brighton took the lead with a beautifully crafted goal, Calderon spotted Lopez breaking into the right-hand side of the penalty area and Lopez picked out a low pass which set up Barnes to tap in from very close range.
Soon afterwards, the hosts extended their lead with a goal made in Spain,
Lopez teed up Calderon who whipped in a cross from the right and Orlandi got in front of his marker to thump a header into the roof of the net, leaving Rams goalkeeper Adam Legzdins with no chance.
The roles were almost reversed three minutes after the break when Orlandi's cross was headed wide by Calderon, who failed to make proper contact with the ball.
Jamie Ward, introduced in first-half injury time after Derby's highly-rated teenager Will Hughes hobbled off, sent a 20-yard shot narrowly over the crossbar in the 52nd minute.
Brighton almost went 3-0 ahead after 63 minutes, hitting the visitors on the counter-attack. Lopez, on the right, released Buckley with a perfectly-timed diagonal pass but his shot was blocked by Legzdins.
The Albion striker was denied by Legzdins again soon afterwards, this time from point-blank range, before the rebound was scrambled off the line by a defender.
What had looked like a stroll in the rain suddenly turned into a nervous finale for Poyet's side when Hendrick got a touch to Ward's driven free-kick to divert the ball past Kuszczak.
Brighton saw out the game and potential new Albion signing Leonardo Ulloa, watching from the directors' box, would have been impressed by just about every aspect of the afternoon - except perhaps the weather.