A headed strike from Ryan Swan gave 10-man UCD their vital away goal before a tenacious defensive display earned them a remarkable Europa League passage in Luxembourg last night.
Their match-winner in the first leg at the UCD Bowl last week, 19-year-old Swan stuck again to give his side an early lead at the Stade Jos Nosbaum.
Left-back Sean Coyne then being shown a straight red card on 28 minutes spelled big trouble for UCD.
Dudelange duly stormed back into the game to score twice before half-time.
But try as they might in the second half, the Luxembourgers could find no way past an inspired Niall Corbet as UCD gallantly hung on to record arguably the biggest night in their history.
Collie O'Neill, who only arrived in the Grand-Duchy at lunchtime due to his wife, Jenny, being (still) overdue on their third child, now brings his youngsters to meet Slovak side Slovan Bratislava in the second round next week.
The club bank another €210,000 to add to the €200,000 secured for qualifying. The game was just 35 seconds old when UCD were awarded a free kick just outside the box after Clayton De Sousa chopped down Jamie Doyle, receiving a yellow card.
Gary O'Neill curled the free kick over the top. It was the early confidence boost UCD would have wanted.
And though Dudelange soon threatened twice through David Turpel, UCD stunned their hosts to take the lead on the night on 17 minutes.
Mark Langtry's throw on the right was flicked on by Doyle for Swan to head home.
Dudelange responded with Turpel shooting into the side-netting from left-back Romain Ney's cross.
Niall Corbet was then well positioned to hold a thumping header from Stelvio Rosa Cruz before going full stretch to his left to palm away a drive from Daniel Da Mota.
The game looked to have fatally turned against UCD on 28 minutes when Coyne was shown a straight red card for a lunging tackle on Kevin Nakache.
Midfielder Dylan Watts was sacrificed as Maxim Kouogun came on in a rejigged back four.
The Students were livid minutes later when Pedro received only a yellow card for what appeared an elbow on UCD central defender Tomas Boyle.
The home side then got right back into the game with two goals at the end of the half.
They levelled on 43 minutes from Joel Pedro whose cracking left-foot drive from 20 yards found the top corner of the net.
Then, three minutes into added time, Dudelange were ahead on the night when Nakache headed home Da Mota's long throw.
Corbett, booked for time wasting just before, came into his own when pushing away a free kick from Rosa Cruz as the pressure mounted.
The busy College keeper then excelled with a brilliant stop with his feet from Ney.
Corbet was there yet again on 64 minutes with another save to turn Rosa Cruz's low shot form distance round a post.
Once more, ten minutes later, Corbet sprung to his right to palm away a drive from Pedro as UCD hung on.
UCD: Corbet; Langtry, Leahy (Harney, 79), Boyle, Coyne; O'Neill; Mulhall, Watts (Kouogun, 31), Benson, Doyle; Swan (Belhout, 67).
Referee: Rahim Hasanov (Azerbaijan).