Shelbourne's Tony McCarthy ruined Longford Town's home debut in the Premier Division before a record attendance of 2,500 at Strokestown Road on Saturday night.
The goal came on 30 minutes when the central defender was left unmarked in the penalty area after Longford Town thought they had cleared a Pat Fenlon free-kick. But the ball was worked back out to James Keddy whose cross was headed home at the near post by the still lurking McCarthy for the only goal of a stop-start, scrappy game.
Shelbourne dominated the match without playing as well as they had in their defeat to Bray Wanderers the previous week.
Longford Town rallied in the final 20 minutes but the fact they managed just one effort on target in the whole game, with Keith O'Connor's half-hit shot being well saved by goalkeeper Steve Williams, said it all.
"Many of my players were a bit nervous and our passing in the first half was poor," said Longford Town manager, Stephen Kenny. "We were edgy and our first touch was not good. But we upped it in the last 20 minutes and showed that our fitness is really good which pleased me.
"Shels are very experienced. When they scored they slowed the game down. They are cute and masters of the 1-0 win.
"We're not despondent. It's no disgrace to lose to Shelbourne. Having said that, we'll not settle for defeat to anyone. We are determined to work harder."
LONGFORD TOWN: O'Brien; Murphy, Smyth, McNally, W Byrne; Notaro, V Perth, S Byrne, Coyle; Farrell, O'Connor. Subs: Gavin for Farrell (62 mins), E. Kenny for Notaro (72 mins), Holt for Perth (78 mins).
SHELBOURNE: Williams; Heary, Scully, McCarthy, Prizeman; R Baker, Fenlon, Doolin, Keddy; S Geoghegan, D Baker. Subs: Haylock for Geoghegan (inj 22 mins), Crawford for Doolin (66 mins), Foran for D. Baker (89 mins).
Referee: P Whelan (Dublin).