A fluid performance from their forward line and a penalty from Daniel Flynn sent St Mary's into the final.
Runners-up in 2009, Edenderry will hope to go one better against St Michael's of Enniskillen, and manager Emmet McDonnell has designs on claiming more silverware.
"We will prepare well. We are a small school trying to build a tradition, but we are glad to be there," said McDonnell.
The foundations for their victory were laid in the opening half as they held a 0-11 to 1-2 advantage at the break.
Sean Doyle landed two splendid points early on and Ger Leech proved solid from frees, but an eye-catching display from 15-year-old Ruarai McNamee who lived up to the family name by causing havoc in the St Jarlath's backline.
"We were a little bit disappointed going in at half-time at 0-11 to 1-2. We felt 0-11 to 0-2 would have been a better reflection of the play. But we knew they were going to come at us (in the second half)," McDonnell said.
But he need not have worried, as Flynn expertly dispatched the 31st-minute penalty and a determined defensive display sealed their spot in the Croke Park decider.
Scorers -- St Mary's SC: G Leech 0-6 (4f), D Flynn 1-0 (pen), S Doyle 0-2, J Dowdall, C McMonagle, M Nolan, R McNamee 0-1 each. St Jarlath's Coll: S Walsh 1-4 (2f), P Glynn, S Silke 0-1 each.
St Mary's, Edenderry -- C Hurley; P Foy, L Flynn, M Kearney; J Dowdall, C McNamee, S Moriarty; D Flynn, D Grehan; C McMonagle, M Nolan, R Caffrey; G Leech, S Doyle, R McNamee. Subs: D Pyke for Caffrey (6), I McKeon for Pyke (22), A O'Connell for McMonagle (54), G Blong for Moriarity (55).
St Jarlath's Coll -- M Mulligan; C Coen, C Langan, R O'Connor; P Glynn, A Nolan, C Cunningham; D Walsh, C Gleeson; M McWalters, L Silke, J Donnellan; S Silke, M Farragher, S Walsh. Subs: J Leonard for D Walsh (27), R Moloney for Donnellan (42), S Glynn for Nolan (57).
REF -- M Duffy (Sligo)