Town were denied a first away win of the season despite leading at the break 4-1.
In a sensational game at Pride Park, Blues looked totally in control at half-time thanks to a brace from Daryl Murphy, an Aaron Cresswell close range finish and Zak Whitbread’s own goal.
Whitbread had scored at the other end for Rams but a recovery looked beyond them until the midlanders surged back into the game after the restart through Craig Bryson.
Jamie Ward reduced the arrears further and Bryson grabbed an unlikely equaliser for the home side two minutes from time.
Mick McCarthy stayed with the same side that beat Brighton on Saturday, the only change in the 18 seeing Tyrone Mings replace Jack Marriott on the bench.
New Derby boss Steve McClaren, having only been appointed at Pride Park yesterday, watched the game from the stands and his new team were stunned twice inside the first 10 minutes.
Christophe Berra challenged Whitbread and the ball cannoned into the net off the Derby defender from Cresswell’s cross for the opener on five minutes and Town fans had hardly taken their seat at the end of the celebrations when Murphy made it two.
Whitbread headed in from a corner a minute later and the mayhem continued on 13 minutes when Cresswell took advantage of more slack defending from the home side to beat Lee Grant from a narrow angle.
Murphy went close to adding a fourth as Town looked likely to score at every foray into the opposition half, David McGoldrick forcing Grant into a save at full length.
Tommy Smith headed over from Paul Anderson’s corner, the Rams looking vulnerable from set-pieces, while at the other end Ward curled a right foot effort wide.
McGoldrick got behind the Derby defence again, his cross hacked clear by Whitbread, the in-form Town striker then dragging his shot wide from the angle.
The fourth came just past the half hour and was a carbon copy of the second, Cresswell’s delivery met by the forehead of the unmarked Murphy, leaving the home fans in a mixture of anger and disbelief.
McGoldrick was inches away from a fifth from Anderson’s cross as confidence swarmed through Town with every touch., Anderson almost galloping clear until Adam Smith’s intervention.
Dean Gerken was forced into a smart save to deny Ward after Anderson had been robbed inside his own box before an amazing first-half came to an end with Town in total command.
Derby made two changes at the break, teenager Mason Bennett and the vastly experienced John Eustace on for Ben Davies and Conor Sammon.
The Rams rallied and Bryson reduced the arrears inside a minute of the restart, sliding the ball home and it needed Gerken to prevent a second goal inside 60 seconds, the ‘keeper denying Bennett from close range.
A well-worked free-kick between Cresswell, Cole Skuse and McGoldrick saw Town’s top scorer fire over as Blues looked to kill the game off, McGoldrick almost getting in again until Grant gathered the loose ball six yards out.
The game took another twist on the hour, the highly-rated Will Hughes prominent in the move and Ward on the end of his cross to bundle the ball in from close range.
Town made a double change on 70 minutes, Carlos Edwards and Jay Tabb on for Anderson and Ryan Tunnicliffe.
Bryson headed wide as the Rams threw everything at Town in search of an equaliser, Blues making a final change with Frank Nouble on for McGoldrick for the last 10 minutes.
Ward tested Gerken from the edge of the box and the fourth home goal of an amazing game came from yet another set-piece, Bryson driving the ball in on 88 minutes after Blues failed to clear.
Town picked up five yellow cards in the second-half of frustration as that elusive first win on the travels slipped away.