The Cahir boys put it up to their more vaunted opponents and led for most of the journey until Dennehy came to the rescue with a well delivered goal after 54 minutes to tie the match at 1-7 each.
While Gael Coláiste looked to the silken skills of Dennehy to carve victory, their opponents had their own scoring hero in midfielder Barry McCormack, who chipped in with a tally of 2-2.
In an eventful first-half Ken Maguire got Cahir off the mark inside 30 seconds with a well-struck point and when the Dennehy brothers, Billy and Declan, turned the tide the other way it looked as if the winners would have matters their own way.
However, Dún-Iascaigh were ready for battle and in 20 minutes McCormack gave the Tralee side something to think about when he rattled in his first goal and points from Enda Flannery and Enda Kendrick had them in a nice position at 1-5 to 0-4 at the interval.
There was another surprise for Gael Coláiste when Flannery stretched Cahir’s advantage immediately on the change of ends before Billy Dennehy and Colm Herlihy sparked Gael Coláiste to life.
Still Dún-Iascaigh put up stout resistance at the back where Kevin Murnane and Tom O’Donnell dealt confidently with whatever their opponents had to offer.
The breakthrough for Gael Coláiste arrived after 54 minutes when Dennehy beat goalkeeper Noel Myles to make for a great finish. Herlihy clipped over the lead point for the Tralee boys but Dún-Iascaigh still refused to lay down arms and Enda Flannery forced an extra 20 minutes.
Once more Dennehy was the guiding light for Gael Coláiste with a snap goal but McCormack was equally up to it and flashed the ball past Gary Kissane at the other end to leave just a point between the teams. It was left to the roving Dennehy to send over the insurance point.
Scorers: Gael Coláiste: B. Dennehy 2-5; C. Herlihy 0-3; B. Long 0-2; D. Dennehy, C. White 0-1 each.
Dún-Iascaigh: B. McCormack 2-2; K. Maguire, E. Flannery, E. Kendrick 0-2 each, C. Dermody, D. Walsh 0-1 each.
GAEL COLÁISTE: G. Kissane; S. Broderick; S. O’Connor; N. McAuliffe; T. Landers; N. Ferriter; E. O’Neill; B. Long; B. Lynch; D. Dennehy; S. Kirwan; T. Corless; B. Dennehy; P. McMuiris; C. Herlihy. Sub: D. White for O’Connor.
DÚN-IASCAIGH: N. Myles; S. Regan; K. Murnane; P. O’Regan; T. O’Donnell; A. Burke; O. Wade; B. McCormack; K. Maguire; E. Flannery; P. Quinn; C. Dermody; M. Grant; D. Walsh; E. Kendrick.
Referee: M. Walsh (Ballyhahill).