A tenth minute goal from Christy Fagan was enough to give St Patrick's Athletic a 1-0 lead to take into next week's First Qualifying Round second leg game against AS Jeunesse Esch of Luxembourg following tonight's game in Richmond Park, Inchicore.
Following a superb start by Liam Buckley's side, the pressure led to Fagan heading in a cross from defender Darren Dennehy to score his fifth all-time goal in European competition for the Saints.
Pat's had further chances to extend their lead in the first half as Graham Kelly headed a chance narrowly wide, while defender Ian Bermingham also went close to adding a second.
However Jeunesse improved in the second half as threatened several times with their best chances falling to Patrick Stumpf who first missed a tap in from three yards on 57 minutes, while the striker was denied by Saints' defender Darren Dennehy who was in the right place at the right time to clear the striker's goalbound header of the Saints' goal line.
Saints' defender did put the ball in the Jeunesse net but his effort was ruled offside as Liam Buckley's side saw the game out to head into next Tuesday's second leg with a one goal lead.
St Patrick's Athletic: Brendan Clarke; Ger O'Brien (C), Darren Dennehy, Sean Hoare, Ian Bermingham; David Cawley, Graham Kelly, Keith Treacy; Conan Byrne (Mark Timlin 60), Christy Fagan, Billy Dennehy.
Subs Not Used: Michael Barker, Dinny Corcoran, Lee Desmond, Pat Jennings, Jamie McGrath, Sam Verdon.