Swansea survived a late Barnsley surge to book a Sky Bet Championship final date with Brentford at Wembley.
The Swans held on for a winner-takes-all shot at Premier League football on May 29 by drawing 1-1 at the Liberty Stadium for a 2-1 aggregate victory.
Matt Grimes had doubled their first-leg lead with a superb strike before half-time, but Barnsley were given hope of turning the tie around when Cauley Woodrow fired home 19 minutes from the end of a full-blooded affair.
Barnsley piled on the pressure in the closing stages but were unable to find the equaliser that would have taken this play-off semi-final into extra time.
Swansea supporters - 3,000 of them - were back inside the Liberty Stadium for the first time in 443 days after the easing of Covid-19 restrictions in Wales.
Barnsley won a League One play-off final between the two clubs in 2006 but they had not scored against Swansea this term, despite having 34 goal attempts in three losing causes.
Tykes boss Valerien Ismael shook up his forward line with Carlton Morris and Victor Adeboyejo replacing Daryl Dike and Dominik Frieser from Monday's defeat at Oakwell.
The opening exchanges mirrored the first leg with space at a premium and neither side able to build up a head of steam.
Andre Ayew, who had settled the first game with a brilliant individual goal, was slipped through by Jamal Lowe but Barnsley goalkeeper Brad Collins charged from his goal to smother well.
Morris had a brief sight of goal at the other end but the opening was snuffed out by Marc Guehi's fine tackle.
There had not been a single attempt on target but that was to change in dramatic fashion after 39 minutes.
Veteran wideman Wayne Routledge, possibly playing his final game at the Liberty Stadium after 10 years as a Swansea player, battled superbly to win a free-kick wide on the left.
Collins punched Conor Hourihane's kick to the edge of the area where Jay Fulton headed the ball into the path of Grimes.
The midfielder was under pressure but some nifty footwork deceived Callum Brittain and he found the corner of the net superbly from 18 yards.
Barnsley responded with a double substitution at half-time as Dike and Jordan Williams were sent on and Brittain switched inside.
Dike's presence gave Barnsley a muscular focal point and Swansea also reorganised after Routledge appeared to extend his knee and had to be carried off.
Barnsley began to risk numbers forward and Freddie Woodman was forced into his first save after 64 minutes, the Swansea goalkeeper pushing away Morris' header from a Callum Styles corner.
Williams was then left unmarked at the far post but Jake Bidwell blocked his shot superbly to leave Ismael holding his head in his hands on the touchline.
But the manager was jumping for joy after 71 minutes as Williams scampered down the right and pulled the ball back for Woodrow to sweep home from the edge of the area.
Swansea substitute Korey Smith should have settled matters when through one-on-one with Collins, but Steve Cooper's side held on and will now have the opportunity to avenge last season's play-off defeat to Brentford.