Kevin McGrath scored the winner in the third minute of injury-time as Coláiste Íosagáin of Portarlington staged an unlikely comeback in Kildare.
First-half goals from Oisín Gill, Stephen Skelton and Conor Ferguson looked to have set Naas on their way to victory and, with 20 minutes to play, the hosts held a nine-point lead.
Shane Lawless' 40th-minute goal brought Íosagáin back into the game and Lawless and Peter Cunningham then scored goals within 60 seconds of each other before helping themselves to a point apiece to put their team ahead with three minutes left.
Naas rallied and wing-back Graham Waters' point looked enough to send the game into extra-time but there was still time for McGrath to strike.
SCORERS -- Coláiste Íosagáin: S Lawless 2-2 (0-2f); P Cunningham 1-2; K McGrath, E Finlay (0-2f) 0-3 each. Naas CBS: S Skelton 1-3 (0-3f); C Ferguson 1-1; O Gill 1-0; R Bergin 0-2 (0-1f); M Sheridan, G Waters, E Ralph (0-1f) 0-1 each.
Coláiste Íosagáin: T Brereton; M O'Reilly, H Weldon, J Hyland; S McGrath, B Crombie, D Barron; P Cunningham, K Bracken; R Galvin, K McGrath, R Reynolds; E Finlay, S McAuley, S Lawless. Subs: R Doyle for O'Reilly (h-t); N Murphy Barron (38).
Naas CBS: D Horgan; C Gill, S O'Hagan, P Gahan; G Waters, O Gill, M Nevin; E Ralph, J Healy; S Skelton, R Bergin, E O'Donovan; M Sheridan, C Ferguson, L Fizgibbon. Subs: D McGarr for Fitzgibbon (47); M Keogh for O'Donovan (47); S Gainey for Waters (60).
Ref -- P Kehoe (Carlow).