Brighton’s draw with Derby means they must beat Middlesbrough on Saturday to be promoted to the Premier League.
Both clubs will aim to join Burnley in the top tier after they secured a top-two finish by beating QPR on Monday.
James Wilson netted a scrappy 95th-minute equaliser for Brighton, who also had Lewis Dunk sent off after Andreas Weimann had put Derby in front.
Brighton are third, level on points with Boro, ahead of their trip to the Riverside on the season’s final day.
A defeat by play-off-bound Derby would not have altered Brighton’s promotion prospects too much, given they have an inferior goal difference to Middlesbrough.
Chris Hughton’s side will go to Teesside without suspended centre-back Dunk, who was sent off with seven minutes remaining for two yellow cards – the second of them coming after a reckless lunge on Craig Bryson.
Anthony Knockaert came closest to opening the scoring for Brighton against the Rams, his first-half free-kick being headed off the line by Jason Shackell.
But Derby looked the more likely of the two sides to find the net, particularly after half-time, and substitute Weimann fired in at the second attempt after David Stockdale had saved his initial shot.
However, Manchester United loanee Wilson turned in the equaliser after a goalmouth scramble from a corner to extend Brighton’s unbeaten run to 13 games.