A disappointing afternoon at Pride Park saw Barnsley comfortably beaten by the Rams in Sky Bet League One.
After going into half time a goal down, following a contentious penalty awarded to the hosts, a limp display in the second 45 was punished by the home side.
It was a very scrappy opening 10 minutes, with lots of aerial duels and very few attempts by either side to get the ball down and play.
However, Derby saw some joy on their left flank through the nippy forward Nathaniel Mendez-Laing, who was giving both Corey O'Keeffe and Jordan Williams some trouble, and it was he who skipped beyond the Barnsley captain to fire in a low cross towards the near post which James Collins - thankfully - stab well wide.
The game then became a little stop-start for a period as the hosts employed some strong-arm tactics, which saw Collins booked for standing on the foot of Maël de Gevigney, before Eirin Cashin flattened Jamie McCart in an aerial challenge that surprisingly saw no card brandished.
From that resulting free-kick, 25 yards from goal, Adam Phillips had Joe Wildsmith scrambling to parry a goalbound strike away from the bottom corner, before Devante Cole's glancing header dropped well wide.
At the other end, Ben Killip had to be sharp as Mendez-Laing struck towards goal after bamboozling his defender, but the Reds stopper turned the shot away.
As we approached the half-hour mark, what looked a over-hit McCart cross had Wildsmith back-pedalling with the former Reds loanee having to tip the ball over his bar, before Max Watters from the eventual corner kick saw an effort deflect just wide of the near post.
Then, with 34 minutes played came the latest in a long line of penalties awarded against the Reds this season, as referee, John Busby apparently saw a foul on Collins inside the six yard box. The striker stepped up to fire home the spot kick and give the hosts a lead they'd take with them into the half time interval.
HALF TIME: Derby County 1-0 Barnsley
The second period began in disastrous fashion for Barnsley, as a deep free-kick from Wildsmith wasn't adequately dealt with by numerous Reds defenders and that allowed veteran centre back Craig Forsyth all the time in the world to beat Killip one-on-one from eight yards out.
Substitute John McAtee - on for the injured Watters at half time - was played through on goal just a few minutes later with a real chance to halve the deficit, but his attempt to bend the ball into the far post was misjudged, with the shot drifting wide.
10 minutes later, it was 3-0 to the Rams. Another deep free-kick not dealt with, Forsyth again in the box on the left, his shot was parried by Killip, up into the air, and fell onto the goalline where Collins simply nudged in.
The hosts could have added to their tally on four obvious occasions. Max Bird somehow sidefooted wide from 12 yards after a teammate had picked him out. Tom Barkhuizen blazed over when through on goal. Cashin headed over from six yards unmarked. And finally, sub Louie Sibley crashed an effort against the crossbar.
The closest the Reds came to scoring was a lovely Fábio Jaló effort - on as a late sub - that curled a yard wide from 20 yards out.
Our first defeat on the road this season was confirmed by the whistle of Busby shortly afterwards, with attention for the Reds now turning to Tuesday night and an Emirates FA Cup first round replay against non-league Horsham in Sussex.
FULL TIME: Derby County 3-0 Barnsley
Killip, O'Keeffe (Cotter), Williams, de Gevigney, McCart, Cadden, Russell, Phillips (J.Benson (Shepherd)), Styles (Jaló), Watters (McAtee), Cole.
Unused: Flavell (GK), Dodgson.
