Their hopes of departing the Championship by way of a glorious Wembley finale are now over and in a remarkable season which should not be overly soured by events at the Liberty Stadium, their journey terminated a game short. But what a journey, still.
There may be no Wembley or Premier League, but - fittingly - Barnsley went down fighting in an inspirational season which has been one of the magical stories in the EFL. They were never going to go quietly.
It looked like they might after Matt Grimes’s fabulous 39th-minute opener, but in the end, it was anything but.
A clinical 15th goal of the season from Cauley Woodrow. The Reds threw the kitchen sink at the hosts in a grandstand finale, but it was not to be.
But those in red jerseys can take pride as can their outstanding head coach Valerien Ismael.
As play-off second legs go, this was a real slow-burner, with neither side piecing together anything substantive in the final third in the first half,
But it was Swansea who always looked the more likely and had a touch more poise and they struck like a viper when it mattered.
It came at almost the exact same juncture as their strike at Oakwell five days earlier and just like in Yorkshire, their goal was a head-turner.
A free-kick on the left from ex-Reds captain Conor Hourihane was punched clear by Brad Collins - without getting a great deal of purchase on his punch - and what happened next was sublime.
Home captain Grimes’s first touch was immaculate when he received the ball just outside of the 18-yard box and he then flummoxed Callum Brittain before curling a beautiful strike past Collins, a moment every bit as eye-catching as Andre Ayew’s effort at Oakwell.
It was deflating in several ways, with the strike actually coming at a moment when Barnsley were starting to look semi-threatening and quietening the home supporters, with a select gathering of 3,000 watching the Swans in action for the first time in 441 days.
Going forward, Barnsley - who threw in a curve ball by offering a shock start to Victor Adeboyejo with Daryl Dike reverting to the bench - lacked care in their use of the ball in half-decent forward positions. The decision-making was not up to much.
Swansea were not earth-shattering themselves but did possess more threat in the shape of the lively Jamal Lowe in particular.
For the most part, it was scrappy and a poor watch, while the Reds got little from referee John Brooks, who punished them on a number of occasions for some soft looking free-kicks, including the one which resulted in the Swans opener when Helik was penalised for his challenge on the recalled Wayne Routledge.
In a tight tie, the breakthrough in the definitive leg was always likely to be huge and it came from the hosts - who had the tie firmly in their grasp and exactly where they wanted it courtesy of Grimes’s superb strike.
Barnsley, whose best moment saw Brittain fire a curling shot wide after Grimes’ opener, had to do something and Ismael, typically, wasted no time at the break and brought on Dike and Jordan Williams for Adeboyejo and Romal Palmer - with Brittain switching to central midfield.
The narrative did not change initially and the energising moment that Barnsley sought stubbornly refused to transpire.
Their best chance to make inroads arrived when Carlton Morris’s header from Callum Styles’s corner was parried by Freddie Woodman and soon after, they finally conjured a flowing move of quality which so nearly resulted in a leveller.
Alex Mowatt, Morris and Styles were all involved, with the latter low cross finding Williams at the far post, but his shot was superbly blocked by Jake Bidwell.
Barnsley did not lose heart and were royally rewarded soon after.
A brilliant break saw Williams bomb forward on the right and his low centre picked out Woodrow, whose finish was unerring.
Finally, it turned into a real contest worthy of a second leg as home supporters became taut and Barnsley finally arrived at the party at the Principality.
Barnsley scented blood with Morris heading off target from Mowatt’s corner and the striker then headed over at the far post following another set-piece.
The visitors pushed and pushed, but it was not to be.
Swansea City: Woodman; Naughton, Cabango, Guehi, Bidwell; Grimes, Fulton, Hourihane (Smith 74); Ayew, Routledge (Roberts 54), Lowe. Substitutes unused: Hamer, Roberts, Manning, Bennett, Latibeaudiere, Dhanda, Cullen, Whittaker.
Barnsley: Collins; Sibbick (Kitching 89), Helik, Andersen; Brittain, Palmer (J Williams 45), Mowatt, Styles; Adeboyejo (Dike 45), Woodrow, Morris. Substitutes unused: Walton, Sollbauer, Halme, Moon, Frieser, Chaplin.
Referee: J Brooks (Leicestershire).