MICHAEL Kightly's superb 65th-minute effort condemned the Reds to defeat on Saturday.
It was caretaker Micky Mellon's second match in charge following the win at Brighton on Tuesday night and, despite a good first-half performance, they were second best after the break.
The result meant Burnley went back to the top of the Championship while the Reds are still bottom, with 14 points from 19 matches.
High-flying Burnley started on top and Sam Vokes twice went close before Barnsley 'keeper Jack Butland palmed away a powerful long-range shot from David Jones.
Danny Ings then headed wide from a fine cross by ex-Red Kieran Trippier.
Barnsley's Paddy McCourt was on top form in the first-half. He set up two fine chances that Tomasz Cywka missed and went on plenty of his trademark runs.
While the Reds played well in the first period, they were dominated after the break and the Clarets deserved their lead when Kightly curled in a fine 20-yard effort after good work from Trippier.
"We missed that clinical finish that's need to get that first goal," Micky Mellon said. "I couldn't fault the players' effort - they gave me everything they have.
"We have to be more clinical and more aggressive in that final third, but there's an awful lot to be pleased about and we'll get better.
"In this situation we're in, some might say we'd have to battle our way out of it.
"I think we can give our players responsibility and play. But we just need to take our chances. We never took them today, hence the result."
* Barnsley will play against Coventry City or Hartlepool United at home in the FA Cup third round on January 4.
