Paul Heckingbottom’s battlers produced a breath-taking comeback in the capital, roaring back from a half-time deficit to secure the silverware.
The Reds were well-deserved victors in the end against Sky Bet League Two high-fliers Oxford United as they went on to secure the most memorable of victories.
And the Reds might not yet be finished at Wembley yet, of course.
The Oakwell faithful will be hoping to return to the iconic venue again next month in the League One play-off final.
With the sun beating down ahead of kick-off, the good news for all the Reds fans who travelled to the capital for their showpiece occasion was that Sam Winnall returned to the starting line-up.
He had shaken off the niggling injury that kept him out of the Reds’ previous two League One games to take his place up front alongside Ashley Fletcher.
Winnall replaced Ivan Toney from the team which started in the gritty league victory at Port Vale eight days earlier, while Lloyd Isgrove was also drafted back in, at Josh Scowen’s expense.
Oxford boss Michael Appleton made four changes to his starting line-up, with JonJoe Kenny, Jordan Evans, Callum O’Dowda and Danny Hylton being drafted into the starting XI following their previous League Two assignment, a 0-0 draw at Cambridge United.
Once the game got under way amidst a raucous Wembley atmosphere, both sides played a cagey opening five minutes.
That wasn’t to last, however.
MORE FROM WEMBLEY
Recalled Oxford striker Danny Hylton tried his luck from distance, only for Marc Roberts to block his strike well.
The Reds responded in kind, with Josh Brownhill’s effort being diverted off target by U’s skipper Johnny Mulins.
Winnall missed a great chance in the 10th minute.
Freed by Isgrove some 30 yards from goal, the Reds’ leading scorer charged through a gap, only to then scoop a strike disappointingly wide from the edge of the box.
There was a scare for the Reds midway through the first period, from a setpiece situation.
Jordan Evans curled in a super curling free-kick from almost 30 yards, with Adam Davies being forced to tip the ball round the post.
At the other end the Reds responded with a trademark effort from Adam Hammill.
The Barnsley talisman fired in a super half-volley from distance which U’s ‘keeper Ben Buchel did well to palm over the crossbar.
It was looking as though the Reds were getting up a head of steam when Oxford broke the deadlock in the 29th minute.
And it was a simply-worked goal which handed the League Two promotion-chasers the advantage.
Winger Alex MacDonald floated over an out-swinging cross from the right, leaving Callum O’Dowda to out-jump George Williams as he headed bravely past a flat-footed Davies.
There followed a five-minute spell of realisation before the Reds hit back in any fashion.
Winnall flicked a volley narrowly wide direct from a Roberts throw-in, while Hammill also tried his luck, dragging a shot across goal and wide from marginally inside the box.
The Reds couldn’t find an equaliser, though they went close when Brownhill fired in a strike from 25 yards that was blocked by Mullins.
At the other end, Oxford’s star striker Kemar Roofe produced a moment of brilliance, firing an overhead kick wide after leaping to meet another out-swinging cross from MacDonald.
The Reds needed a boost early in the second period, and they got just that six minutes after the restart.
Talisman Winnall provided the moment of inspiration, stooping brilliantly to head Hammill’s pinpoint cross home via a deflection off the head of Oxford defender Cheyenne Dunkley.
The Reds were right back in it, and Hammill was screaming for a penalty kick soon after following what looked like a tug in the box from Jordan Evans.
Referee Andy Woolmer quickly waved away appeals.
The Barnsley turnaround was completed in the 69th minute.
This time there was no debating the goal-scorer as Fletcher fired the Reds into the lead.
After sub Toney’s initial shot had been blocked by Mullins, Fletcher followed up to gleefully ram home from close range, and the Reds were into the lead.
The drama continued, however, with ‘keeper Davies producing some real heroics at the other end minutes later.
Davies somehow dived low to his left to beat away a well-struck effort from Liam Sercombe that had looked destined to be evening the match up again.
Hammill then produced another moment of sheer class to all-but wrap up victory for the Reds with 16 minutes to go.
He twisted and turned brilliantly before firing home unerringly into the far corner of Buchel’s net from 25 yards.
Surely the Res were home and hosed at 3-1 up, but no. Oxford roared back to make it 3-2 just two minutes later as Danny Hylton lashed in a bullet header from Roofe’s sweeping cross.
Credit to Barnsley, they kept their foot on the gas in the closing stages as they went for a fourth goal.
Toney saw a shot blocked in what was turning out to be a frantic finale, while defender Alfie Mawson fired in a free-kick which was well saved by Buchel.
Barnsley: Davies, Williams, Roberts, Mawson, White, Isgrove (Scowen, 76), Brownhill, Hourihane, Hammill, Winnall (Toney, 67), Fletcher (Chapman, 90).
Subs not used: Townsend, Bree, Nyatanga, Watkins.
Yellow cards: Toney (90).
Red cards: None.
Oxford: Buchel, Kenny, Mullins, Dunkley, Evans, MacDonald (Maguire, 67), Sercombe, Ruffels, O’Dowda (Waring, 85), Roofe, Hylton (Bowery, 81).
Subs not used: Slocombe, Wright, Long, Ashby.
Yellow cards: Maguire (81)
Red cards: None.
Referee: Andy Woolmer (Northamptonshire).
Star man: Adam Hammill.