The Seagulls ran away from East Perth in the final term of the second semi-final to emerge victorious 10.11 (71) to 7.5 (47) and advance to their second Foxtel Cup decider.
The inaugural winners of the competition in 2011, Williamstown will now face off against reigning WAFL premiers West Perth for the 2014 Foxtel Cup title on Tuesday, July 22.
The champions will receive $100,000 in prizemoney while the runners up take home $40,000.
It was a drama-filled build-up for the Seagulls, who endured four flight delays in the space of 18 hours before they finally arrived in Perth on Tuesday four hours before bouncedown.
After an even opening term, where the half-back lines of both sides controlled the play, it was the Royals that made the first move.
East Perth, who had seven West Coast-listed players in their line-up, kicked four unanswered goals to lead by 16 points early in the second term.
Among those were two clever goals from lively West Coast Eagle forward Josh Hill – including a right foot snap from near the boundary.
But that sparked Williamstown into action and the Seagulls responded with the next three goals to take a narrow lead into half-time.
The lead swapped four times in the third term with the highlight of the quarter being a brilliant running goal to Williamstown’s Jack Dorgan after four bounces.
Both sides missed relatively easy chances in the final term until Williamstown's Anton Woods bounced home a long goal from 50m late in the match to seal the result.
Another Eagles-listed player, Brant Colledge, led the way for East Perth along with Brendan Lee. They each had 17 disposals while big man Paul Johnson was a presence all over the ground.
Former Richmond and West Coast utility Jarrod Oakley-Nicholls was creative out of defence for East Perth.
Hill finished the leading goalscorer on the ground with three as West Coast coach Adam Simpson watched on.
EAST PERTH 2.1 4.2 6.3 7.5 (47)
WILLIAMSTOWN 1.3 4.4 7.5 10.11 (71)
GOALS
East Perth: Hill 3, Carter, McInness, Colledge, Lee
Williamstown: Owen 2, Hetherington, Anastasio, Johnstone, Dorgan, Critchley, Woods, Wyatt, Lambert
BEST
East Perth: Payne, P. Johnson, Colledge, Lee, Hill, Oakley-Nicholls
Williamstown: Lambert, J. Johnstone, Gibbons, Owen, Tighe, Critchley, Mangan
