Amido Balde struck the only goal in the Irish capital as Brendan Rodgers' side were beaten for the first time in six friendly games.
Liverpool lacked threat going forward in the absence of Luis Suarez, although the reappearance of substitute Daniel Sturridge after injury was a promising sign.
Sturridge had been out since May with a damaged ankle but managed 45 minutes and was twice close to a goal, first with a lob and then with a fierce shot into the side netting.
By that stage, Liverpool were behind to a strike from the lively Balde, who turned Andre Wisdom and fired a shot through Simon Mignolet's dive (13).
Liverpool tested Lukas Zaluszka plenty before the break, Stewart Downing and Philippe Coutinho going close, while Sturridge's movement caused problems after half-time.
But the scoreline stayed the same in Liverpool's final game before next week's opener against Stoke.