Barnsley’s victory was their fifth in seven games since a 5-2 home defeat by Forest in November and lifted Paul Heckingbottom’s side up to eighth in the Championship.
Defeat for Forest – a side that has started the year under transfer embargo, are close to a takeover and spent the first day of 2017 warding off an approach from near neighbours Derby for captain Henri Lansbury – left them with just one point from a possible 18 since beating Newcastle on 2 December.
After 25 games, Philippe Montanier’s side are just two points and two places above the relegation places.
Barnsley were bright in a largely scrappy opening half at the City Ground, as Hammill tested Henderson with a free-kick and Scowen sent a close-range effort well over from the resulting corner.
Scowen was also denied by Henderson and defender Thomas Lam in a double chance before the break, and while Forest improved after the restart they failed to register a shot on target.
Nottingham Forest manager Philippe Montanier:
“We are in a precarious position. When you do not win in six games, you are going to move down towards the bottom.
“What is important for us is to continue; the team must have a good mentality. That is important in football.
“I do not worry about my own future. The most important thing is not my future, it is the team and how we work to win the next game. We must focus on that.
“I have not spoken to the new owners yet but I hope the situation will soon become clear.”
Barnsley manager Paul Heckingbottom:
“I think the game was drifting away and heading to a stalemate in the final 10 minutes, we would have taken a point.
“But then it was some goal to win us the game – and that is what we have got in the team.
“We always have to believe we can keep pushing for the win and that is what we do all the time. We focus on how we play, we stick to our game plan and if the breaks come for us from that, then great.
“I was really pleased with the performance, we made changes to bring some energy into the side. We knew we would create chances and I thought we were unlucky not to be in front at half time. We wanted more of the same in the second half, but we also knew that we had firepower available coming off the bench if we needed it.”
Match ends, Nottingham Forest 0, Barnsley 1.
Second Half ends, Nottingham Forest 0, Barnsley 1.
Corner, Barnsley. Conceded by Pajtim Kasami.
Corner, Barnsley. Conceded by David Vaughan.
Attempt missed. Matthew Cash (Nottingham Forest) right footed shot from the centre of the box is close, but misses to the right. Assisted by Hildeberto Pereira.
Hildeberto Pereira (Nottingham Forest) wins a free kick on the left wing.
Foul by Adam Hammill (Barnsley).
Foul by Hildeberto Pereira (Nottingham Forest).
Josh Scowen (Barnsley) wins a free kick in the defensive half.
Goal! Nottingham Forest 0, Barnsley 1. Conor Hourihane (Barnsley) left footed shot from outside the box to the high centre of the goal. Assisted by Adam Armstrong.
Offside, Nottingham Forest. Ben Osborn tries a through ball, but Nicklas Bendtner is caught offside.
Attempt blocked. Hildeberto Pereira (Nottingham Forest) right footed shot from outside the box is blocked. Assisted by Eric Lichaj.