Swindon beat Barnet to seal a 2-1 aggregate win and reach the Johnstone's Paint Trophy final at Wembley.
The hosts took the lead in the first half when Paul Caddis's looping cross found striker Alan Connell who headed past Bees keeper Dean Brill.
Wes Fotheringham denied Sam Deering and Ricky Holmes a second-half equaliser for Barnet, who had Charlie Taylor sent off late on for fouling Oliver Risser.
League Two title chasers Swindon face League One's Chesterfield in the final.
The match on 25 March will be the fifth Wembley final in Swindon's history, and manager Paolo di Canio celebrated with fans, who came on to the pitch after victory over Barnet was secured.
Di Canio's side outclassed the visitors in the first half but it was Barnet who went close early on when Holmes' swerving effort from Mark Byrne's cross hit the side netting.
The Robins powered forward and Caddis's delivery found Connell, who headed home with less than a quarter of the game gone.
Swindon continued to dominate, with Paul Benson twice being denied from close range by Brill, while Raffaele de Vita failed to finish following a blistering run.
The Bees found their stride after half-time but failed to make the breakthrough with Deering's swerving shot from 25 yards their best effort.
Substitute Taylor's high challenge on Risser earned him a straight red and Swindon held on.
VIEWS FROM THE DRESSING ROOM
Swindon Town manager Paolo di Canio told BBC Wiltshire:
"There was a lot of expectation surrounding this game but once again we proved we were the better side.
"It's an amazing night because I couldn't expect the invasion of the fans on the field - it reminds me of when I was young at Lazio.
"The squad are crucial. They are the protagonists and deserve all the credit because they go on the pitch, they run and they challenge for the ball.
"I'm happy for the thousands of people tonight that can go to sleep with a smile and with hope that they are travelling to Wembley with us."