The Reds slip to defeat at Elland Road.
Gianni Alioski's second half tap-in secured the hosts all three points in the Yorkshire derby as the Reds failed to make ground in the battle to survive in the Championship.
José Morais had made a number of changes to his starting XI with Matt Mills replacing the injured Adam Jackson at centre half, Tom Bradshaw started ahead of the dropped Kieffer Moore in attack and there was a first start for Connor Mahoney in midfield.
The Reds started brightly with Gary Gardner firing over from distance on three minutes and forced a succession of corners that United dealt with.
The hosts then were gifted a great opening as Reds defenders got in a tangle just outside their own box and Alioski was through on goal only to clip his effort just wide of goal. It was a big let-off.
But 10 minutes later, a stray pass in midfield allowed Tom Pearce to surge forward unopposed and his shot from the edge of the box somehow found the bottom corner.
The game became scrappy there on in, Ronaldo Vieira entered the book for clattering into Yiadom on halfway.
But with 10 minutes of the half left, Barnsley took control of the game with Brad Potts and Adam Hammill testing the 'keeper, before on 38 minutes, levelling the scores.
After some great work by Hammill, Zeki Fryers fired in a low cross from the left and Leeds youngster Paudie O'Connor deflected the ball into his own net for 1-1.
Right on half time it could have been 2-1 to Morais' side when Mahoney combined with Hammill, danced into the box but saw his left-footed shot turned behind for a corner brilliantly by Peacock-Farrell.
HALF TIME: Leeds 1-1 Reds
A lethargic beginning to the second half was summed up by the second Leeds goal on 50 minutes as Mills failed to beat Kemar Roofe out wide and the former Oxford man raced to the by-line before squaring it for Alioski who had the simplest of finishes to put the Whites back in front.
The Reds had the ball in the net on 55 minutes when Oli McBurnie turned home a Hammill cross from close-range only to see the linesman's flag up for offside.
Morais threw on Moore for Mahoney on the hour mark.
Potts did well to work an opening on 66 minutes, finding room to shoot from the edge of the box only to see the shot deflect off a defender, taking the sting from the shot and going straight at the 'keeper.
George Moncur replaced tom Bradshaw on 71 minutes.
With just over 10 minutes left, another wicked Hammill delivery looked like it was dropping nicely for Moore on the goalline for a tap-in, but somehow the ball stayed out.
Ryan Hedges was the last change, he came on for Mills as the Reds pushed everyone forward.
And as we entered the final stages, a great move released Moncur on the run, he slipped Hammill through into the box, who looked to be fouled by Matt Pennington. The referee blew, but for a Leeds free-kick, booking the Reds winger for 'simulation'.
FULL TIME: Leeds 2-1 Reds
Davies, Yiadom, Mills (Hedges 81), Lindsay, Fryers, Gardner, Potts, Mahoney (Moore 60), Hammill, Bradshaw (Moncur 71), McBurnie.
Unused: Walton, Cavaré, Pinnock, McCarthy.