Carlos Edwards scored an injury-time winner for Ipswich as Derby paid for missing a penalty for the fourth time in a row.
Jamie Ward's spot-kick was saved for the second straight home game after a foul on Richard Keogh by Tommy Smith.
Derby striker Conor Sammon hit the post and Ipswich goalkeeper Scott Loach had to make a string of saves.
But the hosts could not break through and Edwards's long-range strike sealed all three points.
It was a fifth straight clean sheet for the Tractor Boys and an eighth in their last 10 league matches as they extended their unbeaten run to five games.
The defeat ended a series of three successive wins for Derby, who only had themselves to blame after their latest penalty blunder.
After Keogh was adjudged to have been pushed by Tommy Smith following a corner, Ward's low penalty was saved by Scott Loach with his legs.
Derby striker Chris Martin, on loan from Norwich, had the ball in the net just after the hour mark, only to be flagged offside.
Another Derby chance went begging as Jake Buxton's far-post header from Paul Coutts's corner sailed wide.
And the hosts paid the price as Edwards found the bottom corner from 25 yards.
Derby manager Nigel Clough:
"We didn't start as brightly at home as we have been doing but once we got into our stride we played some great stuff and if we score the penalty we come in at 1-0 and take it on from there and could have won the game comfortably.
"That's the last four, so we will certainly look at changing our taker now. When you miss one, you don't mind but when they miss two consecutively... we will change our penalty taker.
"It's a highly unusual stat to miss four on the spin - incredible, really. Me and Andy Garner (Derby coach) are fighting over the next one!
"We will have a chat with the lads and sort it out. Someone will stand up. There's no shortage of volunteers for it
Ipswich manager Mick McCarthy:
"We burgled it. I thought I heard the sirens and I said 'shut the doors, the police are coming!'
"'Did we deserve the three points? Not on that performance because they were better than us.
"We saved a penalty and had to stick at it because we've not played particularly well, but it was a bit of quality at the end - it was a great strike.
"He's 34, Carlos. He's stayed on the pitch and run his socks off and then produces that."
Live Text Commentary
Full Time The referee blows for the end of the match.90:00 +2:40
The assist for the goal came from Guirane N'Daw.90:00 +2:40 Goal scored
Goal! - Carlos Edwards - Derby 0 - 1 Ipswich Carlos Edwards gets on the score sheet with a goal from outside the penalty box to the bottom right corner of the goal. Derby 0-1 Ipswich.89:04
Conor Sammon gives away a free kick for an unfair challenge on Luke Chambers. Scott Loach takes the free kick.88:28
Aaron Cresswell takes a shot from just outside the penalty area clears the crossbar.86:13
Drilled right-footed shot by Jeff Hendrick. Blocked by Jay Tabb.84:50
Direct free kick taken by Jake Buxton.84:50 Substitution
Substitution Ben Davies is brought on as a substitute for Craig Bryson.84:50
Free kick awarded for an unfair challenge on Jeff Hendrick by Frank Nouble.83:58 Substitution
Substitution David McGoldrick leaves the field to be replaced by Michael Chopra.83:58
The ball is crossed by Paul Coutts.82:33
Unfair challenge on Michael Jacobs by Aaron Cresswell results in a free kick. Strike on goal comes in from Chris Martin from the free kick, Jay Tabb gets a block in.81:51
Outswinging corner taken right-footed by Paul Coutts from the right by-line, Richard Keogh takes a shot. Clearance by Richard Stearman.80:27
Guirane N'Daw takes the free kick.80:27 Booking
Booking Craig Forsyth is cautioned by the ref for unsporting behaviour.80:12
Carlos Edwards fouled by Craig Forsyth, the ref awards a free kick.78:53 Substitution
Substitution (Derby) makes a substitution, with Michael Jacobs coming on for Jamie Ward.78:53
Headed effort from inside the area by Jamie Ward misses to the left of the target.78:44
The ball is sent over by Paul Coutts.78:00
Paul Coutts takes a shot. Save made by Scott Loach.
Outswinging corner taken by Paul Coutts from the right by-line, Header by Jake Buxton from deep inside the penalty area misses to the right of the target.71:34
Free kick awarded for an unfair challenge on Carlos Edwards by Craig Forsyth. Free kick taken by Carlos Edwards.69:41
Free kick awarded for an unfair challenge on Craig Forsyth by David McGoldrick. Free kick taken by Frank Fielding.69:21
Corner taken right-footed by Paul Coutts, save by Scott Loach.68:51
Inswinging corner taken from the left by-line by Jamie Ward, clearance made by Luke Hyam.66:34
The referee blows for offside. Frank Fielding takes the free kick.64:09
David McGoldrick takes a shot. Kieron Freeman gets a block in. David McGoldrick gives away a free kick for an unfair challenge on Kieron Freeman. Frank Fielding takes the free kick.62:25
Shot from just outside the box by David McGoldrick misses to the left of the target.61:43
The official flags Chris Martin offside. Scott Loach takes the indirect free kick.59:51
Free kick awarded for a foul by Chris Martin on Luke Chambers. Scott Loach takes the direct free kick.58:18
Indirect free kick taken by Luke Chambers.58:18 Substitution
Substitution Guirane N'Daw is brought on as a substitute for Andy Drury.58:18 Substitution
Substitution Frank Nouble on for Daryl Murphy.58:18
Chris Martin is flagged offside by the assistant referee.56:59
Paul Coutts fouled by Jay Tabb, the ref awards a free kick. Paul Coutts takes the direct free kick.55:10
Daryl Murphy has a headed effort at goal from deep inside the area missing to the right of the target.54:10
David McGoldrick takes a shot. Blocked by Jake Buxton.53:39
Free kick awarded for an unfair challenge on Tommy Smith by Conor Sammon. Luke Chambers restarts play with the free kick.52:26
Unfair challenge on Richard Stearman by Craig Bryson results in a free kick. Direct free kick taken by Scott Loach.51:47
Aaron Cresswell takes the outswinging corner, Paul Coutts makes a clearance.50:32
Inswinging corner taken from the left by-line by Jamie Ward.48:47
Luke Chambers concedes a free kick for a foul on Conor Sammon. Craig Forsyth restarts play with the free kick.48:04
The assistant referee signals for offside against Conor Sammon. Indirect free kick taken by Scott Loach.45:01
The second half has started.45:00 +2:16 Half time
Half Time The ref blows to signal half-time.45:00 +1:25
Carlos Edwards fouled by Craig Bryson, the ref awards a free kick. Scott Loach takes the free kick.44:42
Free kick awarded for an unfair challenge on Richard Keogh by Daryl Murphy. Direct free kick taken by Richard Keogh.44:04 Penalty
A save by Scott Loach from penalty by Jamie Ward. Derby 0-0 Ipswich.42:43
Corner taken by Paul Coutts from the left by-line, Richard Keogh fouled by Tommy Smith, the ref awards a Penalty.40:51
Headed effort from inside the box by Conor Sammon misses to the right of the target.40:08
Outswinging corner taken right-footed by Jamie Ward, clearance by Daryl Murphy.38:29
Free kick taken by Jamie Ward.38:29 Booking
Booking Caution for Tommy Smith.38:22
Unfair challenge on Chris Martin by Tommy Smith results in a free kick.37:45
Paul Coutts takes a shot. Scott Loach makes a save.35:44
Effort from the edge of the penalty box by Jamie Ward goes wide of the right-hand upright.32:59
Effort from outside the area by Craig Bryson goes wide right of the goal.32:00
Free kick awarded for an unfair challenge on Craig Forsyth by Daryl Murphy. Craig Forsyth takes the free kick.31:26
Jeff Hendrick takes a shot. Save by Scott Loach.29:07
David McGoldrick produces a drilled right-footed shot from 20 yards. Frank Fielding makes a save.28:46
Conor Sammon takes a shot. Clearance by Luke Chambers.27:39
Effort from 25 yards by Craig Bryson. Scott Loach makes a save. Inswinging corner taken right-footed by Jamie Ward from the left by-line, clearance made by Daryl Murphy.26:21
Free kick taken by Jake Buxton.26:21 Booking
Booking Richard Stearman goes into the referee's book.26:06
Foul by Richard Stearman on Craig Bryson, free kick awarded.25:07
Free kick awarded for a foul by Carlos Edwards on Conor Sammon. Direct free kick taken by Paul Coutts.22:39
Free kick awarded for an unfair challenge on Richard Stearman by Conor Sammon. Luke Chambers takes the direct free kick.20:21
Free kick awarded for an unfair challenge on Daryl Murphy by Jake Buxton. Aaron Cresswell takes the free kick.16:35
Jamie Ward takes a shot. Clearance made by Aaron Cresswell.12:54
Foul by Jay Tabb on Kieron Freeman, free kick awarded. Kieron Freeman restarts play with the free kick.11:26
Inswinging corner taken left-footed by Aaron Cresswell from the right by-line, Header by Luke Chambers from deep inside the penalty area misses to the left of the target.9:41
Inswinging corner taken right-footed by Jamie Ward, Jay Tabb manages to make a clearance.8:19
Free kick awarded for a foul by Daryl Murphy on Richard Keogh. Direct free kick taken by Frank Fielding.5:13
The ball is sent over by Paul Coutts, Richard Stearman manages to make a clearance.2:53
Aaron Cresswell fouled by Conor Sammon, the ref awards a free kick. Tommy Smith takes the direct free kick.2:20
The ball is delivered by Chris Martin, clearance made by Andy Drury.0:49
The ball is crossed by Jay Tabb, Jeff Hendrick manages to make a clearance.0:00
The match gets underway.
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