With just two points between the sides and Kilburn Gaels desperately seeking to engineer an opportunity for the goal they needed at that stage, wing-back Walsh burst forward to land a monster point.
It was fitting that Walsh should get the game’s final score after he had given the Belfast side a 24th-minute lead they were never to let slip.
Kilburn Gaels’ Keith Killilea had seemingly swung the momentum his side’s way when he plundered his second goal to leave the score 1-7 to 2-3 after 51 minutes.
But Seamus Shannon’s side revealed their character to deny their opponents late on with some tenacious defending and Michael Armstrong put his side two up with three to play before Walsh’s late heroics.
It was a scrappy opening 30 minutes. The rain that began to fall after the junior final undoubtedly affected shooting, and there were a number of wides on both sides.
Killilea got the only score from play in the first half as O’Donovan Rossa, through two points from Sean Shannon and one each from Walsh and Stephen Shannon, led 0-4 to 0-2 at the break.
Two minutes after the restart, Stephen Beatty snapped a long ball and finished to the net, and even at that stage it looked like a decisive score.
But Kilburn Gaels rallied and Killilea brilliantly found the top corner after being picked out by Mark O’Dwyer to reduce the deficit to two points.
Walsh put his side three ahead on 47 minutes before midfielder Deaglin Murphy stretched the lead to four with 10 minutes left.
Killilea found the net from a tight angle a minute later but the Ulster side didn’t panic and the scene was set for Walsh to brilliantly secure the title.
Scorers for Kilburn Gaels: K Killilea (2-1), S Lambert (0-1, 0-1 free), H Vaughan (0-1).
Scorers for O’Donovan Rossa: G Walsh (0-3, 0-1 free), S Beatty (1-0), Sean Shannon (0-2, 0-2 free), Stephen Shannon (0-2, 0-2 ‘65s’), D Murphy, M Armstrong (0-1 each).
KILBURN GAELS: K Finnegan; C Hickey, L Gaule, C McAlinden; N Brophy, B Regan, K Kennedy (capt); H Vaughan, B Kiely; S Lambert, J Egan, M Duggan; K Killilea, M O’Dwyer, P Kennedy.
Subs: A Power for P Kennedy (29), N McDonnell for Kiely (39).
O’DONOVAN ROSSA: C McDonnell; C Orchin, E O’Neill, K McDonnell; Stephen Shannon, C McClelland, G Walsh; C McElhatton, D Murphy; S Beatty, C McGuinness (capt), M Armstrong; A Orchin, T Morgan, Sean Shannon.
Subs: J McGuinness for McElhatton (21), M Turley for McGuinness (31), G Bell for O’Neill (47), C McVeigh for Sean Shannon (55).
Referee: T Carroll (Offaly).