Andy Gray scored two first-half goals as Barnsley earned a hard-fought victory over Leicester City.
Gray prodded home Danny Drinkwater's superb cross after 12 minutes to put Barnsley ahead.
However, just three minutes later Lloyd Dyer equalised for Leicester with a clinical finish from Matt Mills' ball over the top.
Gray then got the winner before the break when he headed home another Drinkwater cross.
Barnsley had won only one of their previous six matches but they showed no lack of confidence as Gray pounced early on after Drinkwater and Ricardo Vaz Te combined to create the chance.
Leicester were targeting back-to-back league wins for the first time this season so they were desperate to push forward and got their reward when Dyer fired in after running onto Mills' expertly timed ball over the top.
David Nugent was a threat leading the line but the Foxes failed to create a clear-cut chance before Gray got his second and what turned out to be the winner as he dived down to head home Drinkwater's cross.
Barnsley should have had a third after the break but Kasper Schmeichel got down to save at the feet of Vaz Te.
Nugent then hit the bar with a header for the hosts before Vaz Te struck over.
Dyer worked an opening late on to grab a dramatic equaliser for the hosts but he couldn't keep his effort down.
Leicester City manager Nigel Pearson:
"They were better than us and that maybe shows us where we are as a club. The expectations are high, of course, but our inability to beat them or create enough goalscoring opportunities was a real problem for us.
"The squad is not as big as people think it is. I hope to rectify that in this window, if we can do business.
"The goals we conceded were poor, both on the counter-attack. They were avoidable and it was sloppy play from us. When your keeper is your best player, that shows you where you are at, in many ways."
Barnsley manager Keith Hill:
"It was a great win and a great performance. I thought the lads were excellent. We came up with a game-plan and it worked, so job done.
"We probably could have won by more in the second half. You expect the home side, with the players that they have got, to expose themselves to the counter-attack, which did leave opportunities for us."