Theo Robinson fired Derby to a third straight victory as the Rams' charge towards the play-off places continued at Hull's expense.
Robinson curled home the game's only goal from just inside the penalty area 32 seconds into the second half.
Derby goalkeeper Frank Fielding kept out shots from Jack Hobbs and Matty Fryatt in the first half.
And as Hull threw everything at Derby in the last 20 minutes, Fielding was on hand to save Fryatt's header.
Despite the late onslaught, Hull succumbed to their third defeat in a row over the Christmas period, leaving them clinging on to sixth place, just one point clear of Blackpool.
Hull had dominated the first half and were stunned when the visitors took the lead moments after the restart.
James Bailey crossed from the left and, after dancing clear on the left-hand side of the penalty area, Robinson curled a left-footed shot beyond Adriano Basso for his seventh goal of the season.
Buoyed by the breakthrough, the Rams enjoyed their best spell of the game, with striker Jamie Ward and midfielder Paul Green going close.
But Hull responded with a spell of unrelenting pressure as Andy Dawson headed Cameron Stewart's cross over the bar and Robert Koren lashed a long-range shot straight at Fielding.
The away side's keeper was on hand to deny Fryatt and Koren in the last 10 minutes as Derby held on to move into ninth place.
Hull caretaker manager Nick Barmby: "At half-time we told the players that Derby had come to frustrate us, but we were done by a sucker punch.
"They scored the goal and then parked the bus, but all credit to them as they did it well.
"Our passing wasn't fluid and we didn't create too many chances. Our reputation's out there as a good passing side, but we've got to make things happen."
Derby first-team coach John Metgod: "The senior players and the younger players have done an amazing job and the team is gelling.
"It might not have been the best performance football-wise. On the ball we were very poor.
"But we changed our system to 4-3-3, got a goal and then we limited them to shots from the edge of the box and they didn't create a real chance."
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Live Text Commentary
Full Time The referee signals the end of the game.90:00 +4:44
The referee blows for offside against Tamas Priskin. Jack Hobbs takes the indirect free kick.90:00 +4:08 Booking
Booking Jason Shackell is cautioned by the ref for time wasting.90:00 +3:15
Robbie Brady crosses the ball, save made by Frank Fielding.90:00 +1:47
Tamas Priskin is flagged offside by the assistant referee. Liam Rosenior takes the direct free kick.90:00 +0:47
The referee blows for offside. Liam Rosenior restarts play with the free kick.90:00 +0:29
Unfair challenge on Craig Bryson by James Chester results in a free kick. Free kick taken by Frank Fielding.89:25 Substitution
Substitution Jake Buxton comes on in place of Jamie Ward.86:23
Corner taken left-footed by Robbie Brady, Jason Shackell makes a clearance.86:00
Corner taken by Robert Koren, clearance made by Jason Shackell.85:38
Corner taken by Robbie Brady from the right by-line, clearance made by Jason Shackell.83:05
Andy Dawson crosses the ball, save by Frank Fielding.81:58
Unfair challenge on James Chester by Tamas Priskin results in a free kick. Indirect free kick taken by Adriano Basso.81:29
Free kick awarded for an unfair challenge on Shaun Barker by Cameron Stewart. Free kick taken by Frank Fielding.81:03 Substitution
Substitution Tamas Priskin is brought on as a substitute for Theo Robinson.80:32
Robert Koren has an effort at goal. Save by Frank Fielding.77:55
Direct free kick taken by Frank Fielding.77:55 Booking
Booking James Chester goes into the book.77:47
Free kick awarded for an unfair challenge on James Bailey by James Chester.76:21 Substitution
Substitution Tom Cairney joins the action as a substitute, replacing Paul McKenna.
Paul McKenna delivers the ball, Matt Fryatt takes a shot. Save made by Frank Fielding.73:42
Robbie Brady takes a shot. Blocked by Jason Shackell.73:05
Craig Bryson is adjudged to have handled the ball. Free kick taken by Corry Evans.71:56
Matt Fryatt challenges Paul Green unfairly and gives away a free kick. Indirect free kick taken by Frank Fielding.69:40
Cameron Stewart crosses the ball, John Brayford makes a clearance.69:12
The ball is swung over by Liam Rosenior, clearance by Shaun Barker.68:58
The ball is delivered by Robbie Brady, Jason Shackell manages to make a clearance.67:24
Unfair challenge on Cameron Stewart by Craig Bryson results in a free kick. Andy Dawson produces a strike on goal direct from the free kick.66:32
The offside flag is raised against Theo Robinson. James Chester restarts play with the free kick.65:09 Substitution
Substitution Ben Davies replaces Callum Ball.65:09
Theo Robinson fouled by Andy Dawson, the ref awards a free kick. Frank Fielding takes the indirect free kick.65:00
Andy Dawson crosses the ball, Jason Shackell makes a clearance.64:03
Corner from the right by-line taken by Robbie Brady, clearance made by Paul Green.63:54
Cameron Stewart takes a shot. Blocked by James Bailey.61:49
The ball is delivered by Jamie Ward, save by Adriano Basso.60:55
Robert Koren takes a shot. Comfortable save by Frank Fielding.60:17
Free kick taken by Robert Koren.60:17 Booking
Booking James Bailey is cautioned.59:32 Substitution
Substitution Robbie Brady joins the action as a substitute, replacing Aaron Mclean.59:32
James Bailey challenges Robert Koren unfairly and gives away a free kick.57:51
A cross is delivered by Cameron Stewart, Header from deep inside the area by Andy Dawson goes harmlessly over the crossbar.57:26
The ball is sent over by Liam Rosenior, clearance by John Brayford.56:33
Free kick awarded for a foul by Robert Koren on Jason Shackell. Frank Fielding restarts play with the free kick.55:32
Paul Green produces a right-footed shot from just outside the box that misses to the right of the goal.53:32
Liam Rosenior delivers the ball, Shaun Barker manages to make a clearance.52:16
Shot from just outside the area by Corry Evans goes over the bar.51:09
Gareth Roberts concedes a free kick for a foul on Aaron Mclean. Free kick taken by Liam Rosenior.49:43
Callum Ball fouled by James Chester, the ref awards a free kick. Jamie Ward produces a shot on goal direct from the free kick, comfortable save by Adriano Basso.48:15
Free kick awarded for a foul by Corry Evans on Craig Bryson. Shaun Barker restarts play with the free kick.45:45
Assist by James Bailey.45:45 Goal scored
Goal! - Theo Robinson - Hull 0 - 1 Derby Theo Robinson finds the net with a goal from inside the box to the bottom right corner of the goal. Hull 0-1 Derby.45:01
The second half begins.45:00 +1:07 Half time
Half Time The referee calls an end to the first half.40:03
Liam Rosenior gives away a free kick for an unfair challenge on Jamie Ward. Gareth Roberts restarts play with the free kick.39:40
Short corner taken by Robert Koren from the left by-line.39:11
Paul McKenna sends in a cross, Matt Fryatt takes a shot. Save made by Frank Fielding.37:52
A cross is delivered by Aaron Mclean, John Brayford makes a clearance.36:14
The offside flag is raised against Aaron Mclean. Direct free kick taken by Frank Fielding.36:06
The ball is sent over by Liam Rosenior, Shaun Barker makes a clearance.34:15
The ball is delivered by Cameron Stewart, blocked by John Brayford.33:49
Paul Green gives away a free kick for an unfair challenge on Matt Fryatt. Direct free kick taken by Robert Koren.31:25
Matt Fryatt gives away a free kick for an unfair challenge on Shaun Barker. Frank Fielding takes the free kick.30:11
Shot by Jack Hobbs from 18 yards. Save made by Frank Fielding.29:37
Outswinging corner taken from the right by-line by Robert Koren.29:29
Centre by Aaron Mclean, Gareth Roberts gets a block in.27:58
The ball is swung over by Robert Koren.27:39
Short corner taken by Robert Koren from the left by-line.27:31
Andy Dawson sends in a cross, Theo Robinson gets a block in.26:09
The referee blows for offside against Callum Ball. Indirect free kick taken by Adriano Basso.25:04
Callum Ball challenges Andy Dawson unfairly and gives away a free kick. Direct free kick taken by Adriano Basso.23:14
Free kick awarded for an unfair challenge on Jack Hobbs by Callum Ball. Direct free kick taken by Adriano Basso.21:31
Theo Robinson is flagged offside by the assistant referee. Jack Hobbs takes the indirect free kick.20:27
The referee gives a free kick against Cameron Stewart for handball. Frank Fielding takes the indirect free kick.19:34
Centre by Liam Rosenior, Aaron Mclean takes a shot. Save made by Frank Fielding.18:49
Corner taken right-footed by Robert Koren.18:37
Matt Fryatt takes a shot. Blocked by Shaun Barker.16:18
Paul McKenna concedes a free kick for a foul on Paul Green. Free kick taken by John Brayford.15:32
The assistant referee signals for offside against Callum Ball. Direct free kick taken by Adriano Basso.15:25
Jamie Ward delivers the ball.15:02
Unfair challenge on Robert Koren by James Bailey results in a free kick. Paul McKenna takes the direct free kick.12:27
Outswinging corner taken right-footed by Robert Koren from the right by-line, Header from deep inside the penalty area by James Chester goes harmlessly over the crossbar.9:04
Free kick awarded for a foul by Matt Fryatt on Craig Bryson. Free kick taken by Frank Fielding.8:46
Matt Fryatt takes a shot. Blocked by John Brayford.8:19
James Bailey produces a drilled left-footed shot from 20 yards. Save made by Adriano Basso.7:52
Gareth Roberts takes the free kick.7:52 Booking
Booking Liam Rosenior is shown a yellow card for unsporting behaviour.7:34
Free kick awarded for a foul by Liam Rosenior on Jamie Ward.7:15
Shot from 20 yards from Robert Koren. Frank Fielding makes a comfortable save.6:02
A cross is delivered by Jamie Ward, James Chester makes a clearance.2:38
Corner taken by Robert Koren from the right by-line played to the near post.2:13
Robert Koren takes the outswinging corner, clearance made by Craig Bryson.1:57
Andy Dawson takes a shot. Shaun Barker makes a clearance.0:15
Unfair challenge on Jamie Ward by Liam Rosenior results in a free kick. Jamie Ward crosses the ball from the free kick right-footed from left wing, Corry Evans makes a clearance.0:00
The game kicks-off.
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