Reading substitute Adam Le Fondre scored an injury-time winner to snatch all three points away from Leeds United at the Madjeski Stadium.
The hosts' night started badly when Jem Karacan had to leave the pitch on a stretcher after just five minutes of the match.
Danny Williams forced the game's first opening, but Paddy Kenny was equal to the midfielder's effort.
Danny Guthrie and Alex Pearce both earned bookings as the home side disrupted Leeds's rhythm with a number of robust challenges.
Despite Leeds having a lot of the ball, it was Brighton who continued to forge out the better chances. Sean Morrison should have done better than glance his header wide from a good Royston Drenthe delivery.
The same combination almost brought the contest's first goal a minute after the break, but Morrison's header flew just over the bar.
Luke Varney and Ross McCormack both came close for the hosts, as their efforts fizzed just over the bar, although Leeds were forced into strikes from distance as they struggled to break down the Royals.
With the game meandering towards a 0-0 finish, Stephen Warnock picked up his second booking for a late challenge, and from the resulting free kick, Le Fondre bundled the ball home to send the home fans into raptures.
