Luke Varney took just eight minutes to make his mark for Town and maintain Blues’ impressive record at the iPro Stadium.
The former Rams striker, who was introduced as a half-time substitute, provided the only goal of the game on 53 minutes, his shot evading Scott Carson to leave Town unbeaten in 10 years at Derby.
The Rams had their chances but the Blues’ defence held firm and when it was breached, Bart Bialkowski came to the rescue, including a save with a last kick of the game from Nick Blackman when a goal looked certain.
Town made two changes to the side that went down so cruelly at Reading on Friday, injured duo Freddie Sears and Tommy Smith replaced by Conor Grant and Adam Webster.
Webster was immediately in the action, denying the dangerous Matej Vydra with a terrific block inside the Town box, then showing the other side of his game with a run down the right flank that beat two Rams, his pass aimed at Brett Pitman cut out by Richard Keogh.
Town were indebted to Bialkowski’s agility on 12 minutes when he got down superbly to prevent Vydra’s shot finding the net after Blues had failed to clear Cyrus Christie’s cross.
Jonas Knudsen held firm as Vydra tried to weave his way to goal, Grant Ward then exchanging passes with Grant before firing wide from distance at the other end.
Carson held on to Luke Chambers’ cross under pressure from Pitman as Blues began to grow into the game, Kevin Bru and Grant combining well to create an opening for the Mauritius international, his acrobatic shot blocked by the Rams’ rearguard.
Craig Bryson tested Bialkowski from the edge of the box with a dipping volley, then Ikechi Anya and Marcus Olsson created an overlap down the left, Knudsen doing enough to kill the danger from the cross.
Cole Skuse’s block prevented Bryson getting in, the midfielder then dragging a right foot effort wide of the post as the hosts turned up the pressure on the Town goal.
Chambers cleared from Anya, then James Wilson’s shot was forced behind for a corner, Christie sending a header wide from the flagkick as Derby searched for the opener.
Will Hughes’ willingness to run at Blues earned a free-kick 25 yards out, Jacob Butterfield sending his effort just wide then Bialkowski saved low to his left from Wilson as Town held on to the break with the goal intact.
Mick McCarthy changed things up at the break with Tom Lawrence coming on for his debut, Grant making way and Varney replacing Bru.
Bryson fizzed a right footer wide, Christie over from distance as the Rams tried to prise the Town defence open but it was Blues who struck eight minutes into the second-half, Varney spinning away from his marker and his left foot shot was only half saved by Scott Carson, the ball drifting into the net.
Former Blue, Darren Bent, entered the fray just past the hour in Derby’s first change, Ward heading over from Lawrence’s cross as Town threatened a second.
Bialkowski plucked Olsson’s free-kick out of the air, Skuse making way for Teddy Bishop for the last 20 minutes in Town’s final change.
Webster blocked Butterfield’s effort, then Hughes was inches wide with a right foot drive from the edge of the box, Butterfield seeing another strike cannon back to safety.
Bialkowski held firm again from Hughes’ teasing cross as the minutes ticked away for the home side, Varney denied for Town as he tried to weave his way to goal.
Bent shot high and wide after the ball fell back into his path 15 yards out but as the final whistle beckoned Blackman looked certain to grab a last gasp equaliser until Bialkowski’s intervention.
Derby: Carson, Christie, Bryson, Keogh, Anya, Wilson (Bent 62), Pearce, Butterfield, Hughes, Vydra, Olsson (Blackman 87). Subs not used: Mitchell, Shackell, Ince, Baird, Johnson.
Town: Bialkowski, Chambers, Knudsen, Berra, Skuse (Bishop 72), Pitman, Webster, Bru (Varney 46), Ward, Douglas, Grant (Lawrence 46). Subs not used: Gerken, Emmanuel, Kenlock, Best. Booked: Skuse, Berra, Varney.
Att: 26, 425