The Reds escape the drop at Griffin Park with another injury time winner, seeing off promotion-hunting Brentford on the final day.
A 91st minute Clarke Oduor goal in West London settled a dramatic evening on the final matchday of the 2019/20 Sky Bet Championship season.
Seeing off their hosts 2-1 in front of the Sky Sports cameras, coupled with results elsewhere meant that Barnsley survived relegation and pulled off one of the greatest of escapes.
Reds' Head Coach, Gerhard Struber had chosen to name an unchanged starting lineup for this crunch clash, having seen his side edge out Nottingham Forest last Sunday afternoon.
It wasn't easy going for the Reds as the Bees dominated the early stages, keeping possession well and seeing an Emiliano effort dragged wide after some great build-up play involving the always-impressive Said Benrahma.
The Algerian playmaker was lively throughout and on five minutes he tricked his way into space on the left and his ball in looked inch-perfect for 25-goal striker Ollie Watkins but Mads Andersen was in inspired form once more and he got a crucial head to the cross to divert it away from the waiting forward.
Barnsley then showed some attacking intent with a marauding Kilian Ludewig finding Luke Thomas whose run into the box and fierce ball across wasn't held by Bees 'keeper David Raya but sadly for the Reds, the ball fell kindly for Brentford who cleared.
This seemed to lift the Reds who began to settle down and get on top of their hosts and on 21 minutes Andersen met an Alex Mowatt free-kick inside the six yard box but couldn't keep his header down.
A minute later and Marcel Ritzmaier made a fine overlapping run down the left before picking out the onrushing Ludewig at the far post but the young German didn't get enough on his shot to trouble Raya in the Brentford goal.
Some clever exchanges in the Bees midfield released Benrahma just after the half-hour mark and he looked certain to score, receiving the ball inside the penalty area and trying to drive it low into the bottom corner but Jack Walton was down smartly to push the shot away.
Referee, Robert Jones didn't then award the Reds a blatant penalty as former Barnsley man Ethan Pinnock clearly handled inside the box, but seconds later a cross wasn't cleared well by Pontus Jannson, the ball fell to Callum Styles and the midfielder drilled in a terrific finish to register his first goal for the club and provide Barnsley a priceless lead.
Just before the break, Walton came to the Reds' rescue once again, somehow turning a Bryan Mbeumo shot onto the post when the home side looked certain to level the scores.
HALF TIME: Brentford 0-1 Barnsley
Barnsley don't sit on leads and started the second half in fine, attacking style, with Thomas bursting through midfield at pace before releasing Jacob Brown but as the forward was about to take aim inside the box, there was Pinnock to slide in and block the shot.
Elliot Simoes returned from injury, taking the place of Thomas just before the hour-mark, but it was Brentford who were now in the ascendancy, with Pinnock heading over a free-kick and then seeing Josh Dasilva fire at goal only to see it blocked well by the covering Michael Sollbauer.
Ritzmaier was clearly felled in the box at the other end, but again, referee Jones was having none of it, much to the bemusement of all inside Griffin Park.
Dasilva would have more joy moments later, however. After Benrahma had somehow skipped through a number of Reds challenges, making real progress and then seeing a pass blocked, but only into the path of Dasilva and the 21-year-old midfielder planted a superb effort into the far corner from 18 yards out.
With 10 minutes remaining, Benrahma dazzled defenders once more on the left before putting over the perfect cross for the ready and waiting Watkins, but the prolific striker somehow fluffed his lines, failing to connect from eight yards out. It was a huge chance, and a real let-off for Struber's side.
With five minutes left on the clock, Ritzmaier and Conor Chaplin were replaced by Oduor and Cauley Woodrow as the Reds looked for fresh impetus, and soon after that, Ludewig made way for last weekend's match-winner, Patrick Schmidt.
And one minute into six added at the end of normal time, the substitutions paid off as Schmidt worked his way into the box on the right-hand side, then cut the ball across for an unmarked Oduor who - like Styles in the first half - slotted home his first goal for the club which sparked dramatic scenes of celebration amongst Reds players and staff.
It was a typical Reds performance under Struber. One of fight, passion and effort. A truly collective effort at that, and as the full time whistle blew, Barnsley were confirmed as safe, finishing 21st in the division and now preparing for another year in the second tier.
FULL TIME: Brentford 1-2 Barnsley
Walton, Ludewig (Schmidt), Sollbauer, Andersen, J.Williams, Styles, Mowatt, Ritzmaier (Woodrow), Thomas (Simoes), Brown, Chaplin (Oduor).
Unused: Collins, Halme, Bähre, Wolfe, B.Williams.