Inspired by a superbly struck 65th-minute goal from striker Robbie Martin, UCD recorded their first win of the season to prevent Waterford United from going clear at the top of the Premier Division table.
Former Ireland manager Mick McCarthy was an interested spectator at the Belfield Park encounter - focus of attention for the Sunderland boss was the Waterford striker Daryl Murphy.
But it wasn't the Irish under-21 international's most memorable performance, as he was closely marshalled by the experienced Tony McDonnell.
UCD, who had scored just one goal in their previous four games, threatened early on when striker Damien Dupuy had a header grabbed by goalkeeper Patrick Holden. And it was the former Galway United man Dupuy again on 10 minutes with a cross from the left headed just wide by winger Anto Murphy.
However, gradually, Waterford United began to get to grips with the game and Steve Yelverton set up a chance for Murphy. His first effort was parried by Darren Quigley and the UCD goalkeeper again performed heroics to push Colm Heffernan's effort from the rebound around the post for a corner.
UCD eventually got their noses in front after 65 minutes when Dupuy supplied a perfect ball to Pat McWalter on the left. His precise low cross was volleyed home by Martin from 12 yards into the net giving goalkeeper Holden no chance.
Showing a greater sense of urgency after that setback, Waterford introduced substitutes Willie Doyle, Seán Finn and Kevin Waters. But the nearest they came to an equaliser came when Heffernan and Finn were wide with long-range efforts.
UCD: Quigley; Mahon, McDonnell, McNally, O'Donnell; Anto Murphy, Hurley, Dicker, McWalter (Kierans, 83 mins); Martin, Dupuy (Sammon, 83 mins).
WATERFORD UNITED: Holden; Andrews (Waters, 66 mins), Doherty, Purcell, Frost; Yelverton (Finn, 66 mins), Reynolds, Mulcahy, Heffernan; Bruton (Doyle, 59 mins), D Murphy.
Referee: T Kelly (Athlone).