A fantastic first-half strike from former Cork City striker Mark O’Sullivan proved the difference as Avondale United lifted the FAI Intermediate Cup for the seventh time in 14 years.
The Munster Senior League side endured a barrage of pressure from the Dubliners in the second half, including eight nerve-jangling minutes of injury time, to seal the win.
Crumlin were heavily-fancied favourites going into the tie, having been unbeaten in the league all season, but Martin Loughran’s side were outfought during a tense opening half.
O’Sullivan had already given warning of his threat when he got on the end of Jack Walsh’s pass and ghosted between the Crumlin centre-halves, but his finish let him down.
It was a warning Crumlin didn’t heed, however, as they failed to close down O’Sullivan as he ran from deep and arrowed a shot into the bottom corner from south of 20 yards.
Crumlin should have levelled early in the second half as striker Jake Donnelly showed great strength to hold off two defenders but, leaning back, he shot over.
The striker saw his shot hit the side netting shortly afterwards, while Walsh was wasteful with a header from David O’Leary’s cross on a rare second-half attack for Avondale.
Donnelly was subject to some rough treatment throughout and he shook off a knock to the head but he went off with what looked a serious knee injury following a bad tackle from Walsh.
He was replaced by Liam Brady – one of two brothers, along with full-back Gareth, of Ireland international Robbie in the Crumlin side.
Brady’s smart nutmeg on Ryan Hogan almost a leveller, but Vinnie O’Brien cleared off Conor Murphy’s toe.
Crumlin had one final chance deep in injury time as Alan McGreal’s corner found Thomas Hyland unmarked, but the captain turned his header wide of the target.
Sean Barron; Dave Kiely, Mark Horgan (Vinnie O’Brien 79), Hughie O’Donovan; Danny O’Connell, Goghan Lougheed, Brian Murphy (Cathal O’Neill 90+4), David O’Leary (Karl Caulfield 64), David Shovlin (Ryan Hogan 35); Mark O’Sullivan, Jack Walsh.
Michael Quinn; Sean Harding, David Brady, Thomas Hyland, Gareth Brady; Craig Walsh, John Sullivan, James Lee, Alan McGreal; Conor Murphy (Sam Burgess 90+2), Jake Donnelly (Liam Brady 74).