It's a priceless three points for the Reds as the fight for survival goes to the last day!
Strikes in each half from Kieffer Moore and Oli McBurnie were enough for Barnsley as they brought their chances of remaining in the Sky Bet Championship back into their own hands.
Moore's cross-cum-shot flew into the net via the far post on 10 minutes, and McBurnie's header on 50 minutes from Adam Hammill's inswinging corner doubled the advantage.
Head Coach, José Morais had brought captain Andy Yiadom back into the starting lineup, along with Zeki Fryers, Connor Mahoney and Ethan Pinnock, with young 'keeper Jack Walton making his home debut.
The visitors started the brighter, forcing the Reds back, who looked nervous on what was a huge day in terms of preserving their status in the division.
But they rode their luck a little, before Moore's cross somehow deceived Dan Bentley in the Bees goal, flying over his head and into the net off the woodwork. It was totally against the run of play, but it turned the game in the Reds' favour.
On 25 minutes, Moore could have notched his second when he met Mahoney's right wing cross with power, but the header flashed just wide of the left hand post.
The visitors were playing attractive football but creating chances seemed difficult, with Liam Lindsay in particular, a rock at the heart of the Barnsley backline.
HALF TIME: Reds 1-0 Bees
Within five minutes of the restart, it was 2-0.
An Adam Hammill corner from the left was met perfectly by McBurnie, whose downward header squeezed over the line, his 9th for the club in his Oakwell swansong.
The Reds should have added a number of other goals, with Moore guilty of passing up two or three great opportunities. Mahoney's great jinking run saw him fire a shot at goal that Bentley parried, but Moore hooked the rebound over with the goal at his mercy.
Hammill then played him in, just inside the box, but he dragged the finish wide of the post.
Worries that the Reds would regret these missed opportunities were unfounded, as the away side ran out of ideas.
It was a huge and vital result for Barnsley, with next Sunday's final game to come and the chance to stay up back in the Reds' hands.
FULL TIME: Reds 2-0 Bees
Reds: Walton, Yiadom, Pinnock, Lindsay, Fryers, Gardner, Potts, Mahoney (Thiam 87), Hammill (Moncur 91), McBurnie (Cavaré 92), Moore.
Unused: Davies, Pearson, Bradshaw, Mallan.