Two goals from Polish international Grzegorz Rasiak and a fifth of the season by Tommy Smith gave George Burley's team a deserved victory and the winning margin could have been even bigger.
Derby's forward play was outstanding and Brighton had no answer to the pace and trickery of Marco Reich down their right side.
Seagulls boss Mark McGhee tried to stem the flow of Rams attacks with some tactical changes, but it made no difference as the home side cruised to a win.
It was the first time Derby had won three league games in a row since September 1998, but it could have been different if Leon Knight had not headed over from six yards in the seventh minute.
It proved a costly miss as Derby went in front two minutes later with a well worked goal.
Smith exchanged passes with Rasiak before sliding a left-foot shot from 16 yards past the hand of Michels Kuipers and inside his right-hand post.
Brighton were lucky not to go further behind when skipper Danny Cullip sliced a clearance against the post and Rasiak surprised Kuipers with a dipping cross that bounced off the bar in the 24th minute.
Another Rasiak cross was driven over by Smith, but Derby moved further ahead four minutes after the break.
This time it was Paul Peschisolido who linked well with Rasiak and the Pole placed a low right-foot shot past Kuipers from 12 yards.
Brighton could have got one back when Charlie Oatway had a close-range shot blocked n the 55th minute, but it was the Rams who always looked the more likely team to score.
Rasiak had a glancing header saved by Kuipers but the Dutch keeper was beaten again in the 80th minute when Rasiak headed a Smith cross down and into the bottom right corner from eight yards.
Brighton kept going, but they were well beaten and Derby were well worth another victory that suggests they are moving in the right direction under Burley.