Match ends, Barnsley 2, Nottingham Forest 1.
A Ryan Hedges strike secured Barnsley's first win of the season as they ended Nottingham Forest's 100% start.
Matty Pearson's header put the Tykes ahead during an impressive opening, but Forest switched from five at the back to a 4-4-2 and began to dominate.
Daryl Murphy headed the equaliser from Barrie McKay's cross and McKay, Ben Osborn and Murphy all went close.
But Hedges restored the lead after the break and although Forest remained in control, Barnsley held on.
Forest's desire to continue the attacking approach which brought them a thrilling 4-3 win over Brentford on Saturday saw Barnsley exploit the space behind their wing-backs early on.
Tom Bradshaw, Hedges and George Moncur all threatened after Pearson's header from Moncur's free-kick made it 1-0 inside three minutes.
Murphy did hit the post with a strike almost immediately and, after the change in Forest tactics, his second goal in two games restored parity.
With McKay impressing out wide and Forest's movement, passing and creativity posing problems, Forest looked likely to earn a third league win in three.
But Hedges' low left-footed effort, his third goal in four games this season, made it 2-1 against the run of play soon after the interval.
And a combination of wayward finishing and some smart goalkeeping by Adam Davies, notably when he denied Tendayi Darikwa late on, saw the Tykes earn their first league points.
Barnsley boss Paul Heckingbottom:
"I am delighted. The players have been surprising me.
"I said after the Ipswich game on Saturday we should have won as we played really well, and I said we would have to play better than that and win.
"That is the organisation, the hard work, being in the right places at the right time, showing people the right way, which makes your job easier when defending your own box. I am happy because certain players are further down the line than I thought."
Nottingham Forest boss Mark Warburton:
"We gave an away early goal, but we re-gathered and changed our shape and scored a really good goal.
"I thought we then controlled the game and looked really dangerous every time we went forward.
"We looked so, so good in the final third, but we snatched at the ball too many times, pulled shots wide, had them saved, and we didn't get our rewards."
- 4WilliamsBooked at 87mins
- 7HammillSubstituted forBarnesat 90+5'minutes
- 20PottsBooked at 81mins
- 10MoncurSubstituted forBirdat 66'minutes
- 4MancienneBooked at 30minsSubstituted forTraoreat 45'minutes
- 24VaughanSubstituted forCarayolat 71'minutes
- 10McKaySubstituted forCummingsat 78'minutes
- Tony Harrington
- Shots on Target
Second Half ends, Barnsley 2, Nottingham Forest 1.
Substitution, Barnsley. Harvey Barnes replaces Adam Hammill.
Kieran Dowell (Nottingham Forest) wins a free kick on the right wing.
Foul by Ryan Hedges (Barnsley).
Corner, Nottingham Forest. Conceded by Adam Davies.
Attempt saved. Tendayi Darikwa (Nottingham Forest) right footed shot from the centre of the box is saved in the centre of the goal.
Attempt missed. Jason Cummings (Nottingham Forest) left footed shot from outside the box is close, but misses to the right. Assisted by Ben Osborn.
Joe Williams (Barnsley) is shown the yellow card.
Kieran Dowell (Nottingham Forest) wins a free kick in the defensive half.
Foul by Joe Williams (Barnsley).
Attempt missed. Jared Bird (Barnsley) right footed shot from outside the box is high and wide to the right.
Attempt saved. Kieran Dowell (Nottingham Forest) left footed shot from the centre of the box is saved in the centre of the goal. Assisted by Mustapha Carayol.
Foul by Daryl Murphy (Nottingham Forest).
Adam Hammill (Barnsley) wins a free kick in the defensive half.
Foul by Tendayi Darikwa (Nottingham Forest).
Matty Pearson (Barnsley) wins a free kick in the defensive half.
Brad Potts (Barnsley) is shown the yellow card for a bad foul.
Andreas Bouchalakis (Nottingham Forest) wins a free kick in the defensive half.
Foul by Brad Potts (Barnsley).