Town went down to a first home defeat in five months, with Derby leaping above Blues into the automatic promotion places.
Chris Martin gave the visitors the points in a game of few chances, finding the net after the hour after he capitalised on a header from Tommy Smith that fell short of Bart Bialkowski.
Derby finished the game with 10 men after John Eustace was dismissed for two bookings but Steve McClaren’s side held on as Town suffered a first defeat in 13 games.
Mick McCarthy made two changes from Town’s last Championship game, the win over Charlton, with Cole Skuse missing out through sickness and Jonathan Parr making way for Tyrone Mings. Luke Hyam came into midfield.
Jay Tabb tested Lee Grant inside the first five minutes, the Derby ‘keeper beating out his strike from the edge of the box, Daryl Murphy seeing his effort blocked from the rebound.
Cyrus Christie got his body in the way of a Mings effort as Town pressed for an early opener, David McGoldrick exploding a 25 yarder just over Grant’s bar.
Derby responded, Jordon Ibe’s cross found Johnny Russell, his shot was cleared, Christie sent the follow up just over.
Smith picked up a yellow card for a foul on Russell on the edge of the box, the Scotland international sending the free-kick wide.
Christie weaved inside and out of Christophe Berra but ran the ball out of play after Will Hughes’ clever flick, then McGoldrick had a shot deflected wide.
Richard Keogh had a header cleared from a corner as Derby shaded the play over the first half hour, John Eustace picking up a yellow card for the Rams for a foul on McGoldrick.
Murphy smashed a left foot bullet just over the bar, Smith doing well at the other end to smother the danger from Martin.
Paul Anderson’s free-kick was headed clear in the final exchanges of the opening 45 minutes, Berra doing superbly to keep the scores level at the break with a terrific challenge on Russell as he got on the end of Jeff Hendrick’s pass.
McGoldrick was booked after a scuffle with Eustace, that could have seen the Derby midfielder get a second yellow card after he blocked McGoldrick’s run in the first instance.
Grant had to be alert to his right to keep out Teddy Bishop’s shot at the second-half gone underway, Town having a penalty appeal when the ball hit Keogh as he stopped Tabb’s cross.
Stephen Hunt replaced Tabb but the midfielder hadn’t touched the ball before Derby went ahead, Christie's long kick downfield got held up in the wind and
Smith’s header back to the ‘keeper was read by Martin who clipped the ball past Bialkowski into the empty net three minutes before the hour.
Grant held firm from Murphy’s flick header, Hughes tested Bialkowski at the other end, the Town ‘keeper then saving low down from Russell’s effort.
Hunt’s free-kick was met by Berra at the far post but the defender could only divert his header goalwards and Grant ended the danger.
McGoldrick showed a lovely touch to escape Eustace and burst into the Derby half but he dragged his shot wide, Town then making a second change with Anderson replaced by Noel Hunt.
Kevin Bru was handed the last 20 minutes, Bishop making way as Town continued to freshen it up in midfield.
Mings almost made Stephen Hunt’s clever pass pay as he looked to break into the box, the duo combining again down the left but Keogh was in the right place to clear again.
Hyam became the third Blue to be booked after pulling back Russell, Eustace then seeing red in the first of six minutes of added on time.
Town pressed for an equaliser and Noel Hunt and Bru went close in a frantic finish, Smith sending a header over with the final chance.