North Launceston chased down a 13-point last term deficit to win its first development league flag since 2012.
After kicking the first four goals of the game, Jade Selby's Bombers were gradually reined in and at stages looked in danger of suffering their third nail-biting loss to Kingborough this season.
But Jack Mazengarb's running finish and Ben Elmer's set shot brought North within striking distance before Lachie Cocker squeezed through the winning goal for a 9.8 (62) to 8.8 (56) victory.
Selby said the result proved his players had learned from a semi-final loss to Tigers two weeks ago.
"It's an amazing rivalry and fortunately we got on the right end of it this time," he said.
"Two weeks ago ... we were in front but we stopped.
"Here we were behind and that was the message that went out - we could just tell that they were similar to what we were, so we just kept pushing forward and to their credit they got brave.
"It's been part of our mantra all year to be brave and it was amazing to get there, I'm really proud of them for them and us coaching staff as well."
The Bombers had been on fire early, with a silky Oliver Sanders slotting the game's first from outside 50 before Tom Foon, Dylan Headland and Harry Rand joined in.
TIME TO DECIDE:
At the other end Cooper Sawdy - the forward who denied North a direct path to the grand final - did his best to deny them the cup by kicking one in each of the next three quarters.
Lewis Edwards snapped truly at the six-minute mark of the last term to give the Tigers a 13-point buffer, but the Bombers weren't done.
Ruckman Cody Lowe, defender Andy Potter and best-on-ground winner Connor Pearton helped swing the momentum back and when Ryan Whitney's tackle set up Cocker the Bombers just had to hold out two minutes.
ELSEWHERE IN SPORT
Mitchell Lister's running shot and a deliberate out of bounds call provided nervous moments before the siren sounded deep in Kingborough's forward line.
"It's our fifth consecutive week travelling and I feel like that time really bonded us, we've come together as a collective," 21-year-old Pearton said.
"We know Kingborough at their best they would throw challenges at us, but we thought if we could stick it out and grind it out we thought we could be better for longer and that was our motto for today."
The result denied Kingborough its maiden TSL flag.