Dundalk made the faster start and took control inside the opening half hour. Eoin Kenny struck first at 9'37'', giving the home side an early lead, and Harry Groome doubled the advantage at 28'20'' as Dundalk moved 2-0 ahead. At that stage, the hosts looked set for a comfortable night.
Waterford found their way back just before the break. Tom Lonergan pulled one back on 45'00'', cutting the deficit to 2-1 and giving the visitors momentum going into the second half. That shift carried on after the restart, with Lonergan converting a penalty at 62'38'' to level the match.
The game then swung on a late finish. With Dundalk unable to restore their early grip, John Mahon struck at 84'55'' to complete the turnaround and hand Waterford a dramatic 3-2 victory. It was a sharp reversal from the first-half pattern and a result Dundalk will regret after holding a two-goal cushion.