Ruairi Keating scored the only goal of the game at Richmond Park to revitalise St Patrick's Athletic's season and leave Dundalk in the doldrums at the foot of the table.
The hard-earned victory ended three straight defeats for Jon Daly's Saints.
Stephen O'Donnell's Dundalk, who've now not won on their last seven visits to Inchicore, drew a blank in front of goal for the third match running and have yet to score from play in their four games to date.
St Patrick's made three changes from their 3-1 defeat in Waterford on Monday, Brazilian goalkeeper Marcelo Pitaluga replaced by Danny Rogers while Kieran Freeman and Kian Leavy came in for Conor Kelley and Ryan McLaughlin.
Following their 5-0 home humbling to Sligo Rovers, Dundalk also rang the changes with no fewer than five, chief among them goalkeeper Ross Munro starting in place of George Shevley, having replaced him at half-time on Monday.
And it was the visitors who started on the front foot, forcing an early corner before Ciaran McGuckin warmed the hands of Rogers with a low drive which might have held more venom.
Saints didn't come alive until 13 minutes, Anto Breslin breaking on the left to whip over a dangerous cross which neither Keating or Brandon Kavanagh could apply the vital touch to.
Kavanagh did appear to be bundled over by Hayden Muller, but St Pat's penalty appeals fell on deaf ears.
Referee Ray Matthews further incensed the home faithful, waving play on when McGuckin clearly pushed over Jay McClelland.
Jamie Gullan met the cross with his shot deflected out for a corner by defender Luke Turner.
With the game crying out for a spark to bring it fully to life, St Pat's thankfully provided it when punishing Dundalk on a counterattack on the half-hour mark.
Chris Forrester hooked a ball over the top to catch the Dundalk defence in retreat, with skipper Andy Boyle scrambling back into position having won a header.
Kavanagh showed good control and strength to hold off Muller and lay the ball deftly into the path of Keating.
Though the striker's initial shot was parried by Munro, he followed up to slide home the rebound for his second goal of the season.
Further sloppy defending might have cost Dundalk once again eight minutes into the second half.
A loose header from Louie Annesley dropped for the impressive Leavy, who showed good feet to run on and bring the save of the night from Munro with a left-foot drive.
Kavanagh got forward to trouble the Dundalk defence minutes later before the visitors might have been level on 57 minutes.
Daryl Horgan's left-flank cross found Robbie Benson, who arrowed his header wastefully over the top.
But there had been far more impetus to St Pat's from the resumption and they worked Munro again on 66 minutes.
Forrester got a headed flick to the lively Kavanagh's free kick with Munro batting the ball away to be scrambled clear.
The game opened right up in the final quarter as Dundalk chased an equaliser.
And they might have got it on 78 minutes but for a brilliant last-ditched tackle by Turner on Gullan, who had been played in by Benson.
A minute later, Scott High drilled a shot agonising wide of Rogers' right-hand post while substitute Sam Durrant rifled off target late on to compound Dundalk's frustration.
© rte.ie