Brighton striker Craig Mackail-Smith ended his goal drought as his solitary strike condemned Derby to a fifth straight npower Championship defeat.
The Scotland international opened the scoring in the 13th minute with a fantastic finish into the top corner - his first goal in 10 league games.
Mackail-Smith also hit a post in the closing stages but his strike was enough to help the Seagulls win at Derby for the first time in 27 years.
It also earned Guy Poyet's side a third victory in four games, with the south coast club having goalkeeper Casper Ankergren to thank too for making several fine first half saves.
Fifteen-year-old substitute Mason Bennett almost snatched an equaliser for the Rams but lifted his shot over the bar and despite late home pressure, the Seagulls survived.