Antony Kay's excellent goal three minutes from time gave Barnlsey maximum points and was the only bright note of a poor derby clash against Chesterfield at Oakwell.
The Tykes had rarely troubled the Chesterfield defence throughout an average encounter but with the game coming to its climax, target man Barry Conlon delivered a sublime pass into the path of midfielder Kay, and he dispatched a low drive from just inside the box that earned Paul Hart's men a welcome home victory.
The visitors' misery was compounded by the second half sending off of midfielder Mark Innes, following a Barnsley free-kick on the edge of the penalty area.
Innes was involved in an off-the-ball altercation with Barnsley's lone striker Daniel Nardiello and when the referee's assistant flagged, Innes was shown the red card for retaliation.
Up to that point Chesterfield had looked comfortable enough and seemed on course for a battling away point. But Barnsley fought to the finish and Conlon's inspired piece of creative play enabled Kay to ram home the winner.
The first half was disappointing, with both sides struggling to carve out good chances.
Michael Chopra delivered one decent free-kick that Kay headed straight at Chesterfield keeper Carl Muggleton, while at the other end the lively Jamal Campbell-Ryce gave Barnsley full-back Bobby Hassle a tough time.
Campbell-Ryce almost broke the deadlock on 22 minutes when he cut in from the left but his shot was blocked by Barnsley keeper Nick Colgan.
There was a bad miss by Chesterfield's striker Mark De Bolla seven minutes before the break when he side-footed wide from 12 yards after strike partner Tcham N'Toya-Zoa had attracted three Barnsley defenders to him before providing the pass.