Harps' best opportunity of the first half fell the way of the player-manager, but he fired wide from 18yards after turning onto his right foot and at the close of part one the deadlock remained intact.
Were it not for the sticky conditions, Harps could have grabbed the lead goal in the first minute of the second half with Davitt Walsh's ball across the box sticking in the muddy goalmouth as David Bell watched on agonisingly from his position at the back post.
Dundalk goalkeeper Chris Bennion then turned an effort from Walsh away for a corner before racing out to deny Bell who had been played one-on-one by Gary Crossan.
The Oriel Park outfit got the goal they craved on 77minutes however and it came from substitute Ray Scully. After a neat move down the left, Keith Dunne cut back to Scully who fired home from 12 yards sending the Lilywhite hoards into jubilation as they held out to clinch second spot.
Meanwhile, the home followers filed out a disgruntled bunch once more and they departed Finn Park for the final time this season knowing that their side finished in its lowest league position in over a decade.
Finn Harps: James Gallagher; James Doherty, Jonathan Minnock, Eloka Asokhu, Shane Bradley; Michael Funston, Shaun McGowan, Gary Crossan, Anthony Gorman; Davitt Walsh, Matthew Crossan. Subs: David Bell (for Minnock, h/t); Darren Meenan (for G.Crossan, 76mins).
Dundalk: Chris Bennion; John Flanagan, Brian Kelly, Aidan Lynch, Simon Kelly; Robert Dunne, Paul Marney, Sean Finn, Keith Dunne; Trevor Vaughan, Philip Hughes. Subs: Ray Scully (for Flanagan, 40mins); Chris Doran (for Kelly, 58mins); David Hoey (for R.Dunne, 69mins).
Referee: Richie Winters