Captain Paul McCarthy scored his second goal of the season to fire Wycombe into the second round of the Worthington Cup with their first ever away win over second division rivals Swindon.
Skipper McCarthy headed Wycombe into round two with a dramatic extra-time winner after Swindon defender Adam Willis appeared to have steered the game into a penalty shootout with his second goal in Robin's colours.
McCarthy headed in his second of the season 19 minutes into extra time, nodding the ball past Swindon keeper Bart Griemink after Keith Ryan had crossed from the back post.
Defender Willis thought he had saved Swindon from defeat when he bundled in only the second goal of his professional career to rule out Wycombe substitute Richard Harris' 91st minute opener.
Willis scrambled the ball home from close range after Wycombe's former Swindon keeper Frank Talia had spilled captain Andy Gurney's free-kick.
Substitute Harris had earlier put the Chairboys ahead less than 60 seconds into extra time with a powerful close-range header after Swindon gloveman Griemink had only palled Steve Brown's first-time effort.
Wycombe manager Lawrie Sanchez afterwards paid tribute to his side's battling spirit, saying: "That was a good hard-fought victory.
"It wasn't the best game of football but it was played in a good spirit, and I'm delighted we came through it."
Swindon manager Andy King said: "We are disappointed because we have gone out of the cup, but I was more disappointed with the manner of the defeat.
"We don't seem to be able to score or create any chances at the moment and that is worrying, something we need to put right."