The former Bolton winger caught the Rams cold when he turned in Adam Hammill's cross and that proved to be enough to give the Terriers their second win of the season.
After a terrible start to Saturday's Championship clash at the John Smith's Stadium, Derby played some attractive football but they lacked a cutting edge and were unable to rescue a point which would have been no more than they deserved.
Huddersfield have lost just once since returning to the second tier and look very much at home at this level, with Simon Grayson having blended together a well organised side.
The Derby coach was late arriving after being held up in traffic and Nigel Clough's side were caught napping after just 47 seconds when Huddersfield took the lead.
Hammill was the architect, with the on-loan winger making an instant impact on his home debut as he raced down the right unchallenged and was allowed to pick out the on-rushing Ward, who got in front of his marker and diverted the ball past Frank Fielding with a neat right-foot finish.
The Rams were guilty of some sloppy passing and continued to create problems for themselves but started to get into their stride with some slick passing and movement.
And it needed a great last ditch tackle from Terriers captain Peter Clarke to get team-mate Paul Dixon out of jail after the full-back's poor pass let in Jamie Ward, who laid the ball off to Connor Sammon. Clarke stepped in with a brilliantly timed tackle to deny the big striker as he was seemingly poised to equalise.
Derby continued to dominate possession but Huddersfield looked dangerous going forward and Craig Bryson breathed a sigh of relief when he headed a free-kick wide of his own goal.
Rams boss Clough clearly had a few words to say to his players at half-time as they made a bright start to the second half, but Huddersfield almost doubled their lead when Adam Clayton's drive was tipped around the post by Fielding.
But the Terriers were struggling to keep hold of the ball and Conor Doyle spurned a great chance to equalise when he fired over the crossbar at the far post after a good run from the lively Jamie Ward.
Former Terriers striker Theo Robinson was given a warm ovation when he replaced Sammon with 12 minutes remaining with Derby still enjoying plenty of possession but lacking quality in the final third.
Huddersfield sat deeper as the clocked ticked down and the Rams had a big shout for a penalty deep into stoppage time.
Referee Trevor Kettle waved play on when Jeff Hendrick went down in the area after a strong challenge in the air and the Terriers held on for all three points.