Pat Hoban scored twice as Stephen Kenny's side ended Cork's unbeaten run to climb to the top of the SSE Airtricity Premier Division
Going into this game, Dundalk knew that a win would see them leapforg their opposition and finish Friday night on top of the table, while Cork City were looking to defend their unbeaten start to the season.
The Lilywhites started well, Darren Meenan running through the midfield and striking low and wide. Dundalk's pressure paid off after 10 minutes when Andy Boyle collected the ball from Meenan, before releasing Mountney on the edge of the box. Mountney scuffed his volley but it looped over the despairing McNulty and into the net.
Nine minutes later, Dundalk doubled their lead with Hoban doing well to win a corner. Meenan played it short to Daryl Horgan, and his inch perfect cross was nodded into the top left corner by Hoban.
The Louth side dominated the entire game, with Daryl Horgan tormenting his former club twisting and turning past John Kavanagh and shooting over, before Hoban added his second. Almost a carbon copy of his first, Hoban nodded home after some superb work from Richie Towell on the left wing.
Dundalk picked up where they left off in the second half, with Towell thumping home from the edge of the area five minutes in.
After that Dundalk took the foot off the pedal, but Cork did not put them under much pressure. Mark O'Sullivan and Rob Lehane both saw efforts go wide as every attack from the Rebel Army seemed to be snuffed out by the excellent Boyle.
The result sees Dundalk climb above Cork City to the top of the table, with Cork dropping to second place. However, the Leesiders have a game in hand which could see them return to the summit.