Leon Knight came back to haunt Rangers with the goals which toppled the title favourites.
The little striker, on loan to Brighton for two months from Chelsea, struck twice against the club he had a loan stint with when they were in the First Division.
It continued Brighton's 100 per cent start to the season and lifted Knight's tally to four in two League games.
Rangers finished a miserable night for them with ten men. They had Terrell Forbes sent off on the hour and Clarke Carlisle stretchered off in injury time after they had already used all three substitutes.
The game began well for Ian Holloway's side, Gino Padula putting them ahead in the ninth minute.
The Argentinian full-back delivered an inswinging free-kick from the right wing which went straight in as skipper Steve Palmer failed to connect with a near post header.
The lead for Rangers, however, lasted for only three minutes.
The five foot four inch Knight plunged to nod home a cross from Gary Hart, his third header in two games following an opening day double at Oldham.
Rangers were reduced to ten men on 60 minutes, thanks to a rush of blood by Forbes.
The former West Ham defender reacted to a tackle by Kerry Mayo by head-butting the Brighton full-back.
Mayo was booked for the challenge by referee Mark Warren after receiving treatment for a cut above his left eye.
Knight wasted no time in capitalising on Brighton's numerical advantage.
He latched onto a header from fellow loan striker Darius Henderson to fire the winner on 69 minutes.
Rangers' misery was compounded deep into injury time when central defender Carlisle was stretchered off after colliding with Brighton goalkeeper Ben Roberts.
Knight said: "It is pleasing to get two goals and the three points as well. We knuckled down. They are a big side and we competed with them."