Vic Country looked far too strong early in the game and broke out to a 31-point lead midway through the second term.
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But instead of falling away like they had done previously throughout the championships, the West Australians responded to storm home, winning 9.13 (67) to 10.5 (65) at Etihad Stadium on Wednesday.
Smith's goal with three minutes to play capped an eventful day for the powerful prospect.
Having moved from the back pocket to be stationed deep in attack, Smith was physical and gave away five free kicks.
But he imposed himself on the contest and made things happen around him, evident in his snap around the body from close range, which broke the state's five-game losing streak.
Connor Blakely, a big, tall and strong midfielder who pushes through contests, picked up 23 disposals, eight clearances and six tackles to close his strong championships for WA, while Tyler Keitel played well through defence with 19 touches and six rebounds.
The lively Jarrod Pickett came into the game later, and kicked an important goal in the third term. Taller options Aidan Anderson, Adam Creeper and Jack Cripps all chimed in with two goals, while at the other end Clayton Giblett did a solid defensive job on Vic Country forward Paddy McCartin.
Lukas Webb was a standout for Vic Country, who ended their championships with two disappointing defeats.
If Webb wasn't kicking goals, he was setting them up. The left-footer booted four of his own in a breakout game, and helped others to opportunities as well.
Twice he delivered the pass lace-out to McCartin and whenever Webb had the ball he was clean and unrushed, able to size up his options and make the right call.
Webb gathered 16 disposals and six marks and had plenty of influence, while Jordan Cunico and Rhys Mathieson also finished with 16.
Western Australia's win means the division one title will be decided on Thursday when South Australia and Vic Metro face off at Simonds Stadium.
Metro will need to win by approximately three goals to jump ahead of South Australia on percentage.
Vic Country 4.3 9.3 10.4 10.5 (65)
Western Australia 2.1 5.4 8.7 9.13 (67)
GOALS
Vic Country: Webb 4, McCartin 2, Dixon, Evans, Wilson, Lonie
Western Australia: Cripps 2, Creeper 2, Anderson 2, Palfrey, Pickett, Smith
BEST
Vic Country: Webb, Butler, Mathieson, Goddard, Cunico, Howe
Western Australia: Blakely, Hardisty, Keitel, Smith, Giblett, Garlett
