Wayne Rooney's side, who were deducted 21 points for historical financial mismanagement, looked like they might be able to pull off a remarkable survival after some good form earlier in the season.
But the Rams couldn't do enough to remain in the second tier, despite an incredible job by Rooney, who was forced to sell some key players and make use of the club's youngsters throughout the season.
Rooney's men were beaten 1-0 in west London against a QPR side who have faint hopes of finishing in the play-offs with Luke Amos' 88th-minute goal proving to be the difference.
It looked like Derby might survive another day in the division, with Reading 4-1 down at home to the Swans on 58 minutes at the Madejski Stadium.
However, a remarkable comeback by Paul Ince's side, who have now lost just one of their last six games, relegated the east Midlands outfit.
Goals from Tom Ince and Lucas Joao made it a frantic finish in Berkshire before Tom McIntyre's goal in the fifth minute of stoppage-time earned Reading a priceless point in their survival bid.
The two other sides in the relegation battle, Barnsley and Peterborough, faced each other in Yorkshire, with Posh running out 2-0 winners.
Despite that result, Peterborough now need to win all three of their remaining fixtures and hope Reading lose all of theirs.
Barnsley, who have played a game less than the teams around them, also need to pick up maximum points to avoid relegation to League One.
Both sides need a miracle to remain in the division this season.