Jamie Cureton's dramatic last-gasp winner got Reading's promotion charge back on track and ended a run of three successive defeats.
Cureton pounced from close range after it looked odds on that Derby's disciplined defending was going to earn them a point at the Madejski Stadium.
The Royals dominated for long periods and manager Alan Pardew will be worried by their lack of cutting edge as he bids to guide his side into the Barclaycard Premiership.
Despite Reading's superior possession they struggled to test Derby goalkeeper Lee Grant until Cureton struck.
Sammy Igoe had the first real chance of the game but he dragged his shot from just outside the box wide of Grant's left post.
Moments later Craig Burley had an opportunity to put the Rams ahead but Reading goalkeeper Marcus Hahnemann pulled off a fine save.
Igoe was creating problems for Derby and it was no surprise that his endeavour created the opening goal after five minutes.
The former Portsmouth winger picked the ball up inside his own half and surged forward before picking out Nathan Tyson in space and the youngster slotted home, giving Grant no chance.
The Royals were not ahead for long though as three minutes later Igoe turned from hero to villain when his handball left referee Mike Ryan no option but to point to the spot.
Burley stepped up and lashed home his first goal since October 2001.
McLeod then found space on the edge of the box but his weak shot was easily gathered by Hahnemann.
Pardew was forced to make a change after 22 minutes when James Harper limped off to be replaced by Kevin Watson.
The impressive Igoe forced Grant into another good save on the half hour with a fierce right-footed drive as the Royals gradually started to take control of the game.
Five minutes before the break Cureton should have put Reading ahead but he put his effort from just six yards out was over the bar after a fine cross from Tyson.
Two minutes later Tyson almost put the Royals ahead again but his left-footed drive was superbly turned over the crossbar by Grant.
Reading striker Martin Butler had a great opportunity a minute into the second half but his shot was blocked by Chris Riggott.
On the hour Izale McLeod was presented with a marvellous chance to give the Rams the lead but from just six yards out he somehow managed to shoot straight at Hahnemann.
And 10 minutes later he was presented with another golden opportunity but his weak header from eight yards drifted over the crossbar.
And 15 minutes from the final whistle Watson unleashed a stunning drive from 25 yards that had Grant beaten but was relieved the see the ball rebound off the woodwork and to safety.
Reading's second-half dominance finally told when Cureton grabbed the winner to snatch all three points.
John Salako escaped down the left wing but his cross evaded everyone in the box and Ricky Newman picked the ball up and sent it back into the danger area - where Cureton smashed it home.
Teams
Reading Hahnemann, Murty, Williams, Brown, Shorey, Igoe,
Harper (Watson 23), Newman, Tyson (Salako 79),
Butler (Henderson 71), Cureton.
Subs Not Used: Mackie, Rougier.
Booked: Igoe.
Goals: Tyson 5, Cureton 90.
Derby Grant, Barton, Elliott, Riggott, Mills, Murray, Burley,
Bolder (Evatt 90), Morris, Christie, McLeod (Tudgay 81).
Subs Not Used: Kinkladze, Oakes, Holmes.
Booked: Riggott, Elliott, Burley.
Goals: Burley 8 pen.
Att: 16,299
Ref: M Ryan (Lancashire).