Juninho Bacuna's first league goal for nearly eight months heaped more pressure on Derby boss Phillip Cocu as Huddersfield secured a 1-0 victory.
The midfielder slotted home a clinical 53rd-minute winner as the Terriers claimed their first win over the Rams for almost four years.
Carlos Corberan's improving outfit extended their unbeaten run to four games as they continued to climb the Championship table.
Defeat for the Rams on the road extended a miserable start to the season for Cocu's side, without the self-isolating Wayne Rooney, who have now lost five of their opening six league matches.
Right-back Pipa went close for the hosts in the sixth minute, but his left-footed curler flew wide of the left upright.
At the other end Andre Wisdom, one of three changes in Derby's starting line-up, saw his thunderous long-range effort charged down on the edge of Town's box.
Tom Lawrence, another recalled player, then had a penalty appeal turned down after a clash with Huddersfield skipper Jonathan Hogg in the box.
Kamil Jozwiak, the third and final change to the visitors' line-up which lost 1-0 to Watford on Friday night, also went close, curling a right-footed shot narrowly wide of the far post.
Spanish defender Pipa then tested Rams keeper David Marshall with a fierce strike, but the Scotland international did well to tip the effort over his bar.
Graeme Shinnie dragged a weak right-foot shot wide of the left post when he should have done better in the position.
Wisdom was in the thick of the action again seven minutes before the break, but he smashed a shot straight at Terriers keeper Ben Hamer.
Pipa blasted over from the right edge of the area as the home side came close to taking the lead ahead of the interval.
Josh Koroma tried his luck on the stroke of half-time, but his right-foot show flew high and wide.
The Terriers started brightly following the resumption and could have easily taken the lead, yet striker Fraizer Campbell was unable to get on the end of Harry Toffolo's dangerous delivery into the six-yard box.
But the breakthrough came – and it was Bacuna who made it with a clinical finish.
Some great work from Toffolo down the left saw the wing-back square the ball to Bacuna on the penalty spot. The Dutchman calmly slotted into the bottom-left corner.
And Bacuna nearly turned provider when he teed up fellow midfielder Koroma, but his goalbound shot was deflected wide.
But Derby came within a whisker of equalising with 12 minutes remaining, with Hamer denying Duane Holmes from close-range with a superb one-handed save low to his left.
Town could have netted a second but Marshall tipped Naby Sarr's header over late in the action.
However, the home side breathed a huge sigh of relief when Matt Clarke's diving header from substitute Martyn Waghorn's cross crashed off the post.
