Tomic will take on top seed Juan Martin del Potro in the title match after fighting his way past giant-killing qualifier Sergiy Stakhovsky 6-7 (4-7) 7-5 6-3 in Friday's second semi-final.
Earlier, del Potro thumped Russian fourth seed Dmitry Tursunov 6-4 6-2 in his semi-final to continue his impressive unbeaten start to the summer.
Tomic mustn't have received the news he'd drawn world No.1 Rafael Nadal in the first round of the Australian Open until just before four o'clock on Friday.
It was precisely then that the Australian wildcard was cruising at 3-0 and 40-love in the first set.
Then he suddenly lost his focus, allowing Stakhovsky to hold serve and break back in the seventh game to force the tiebreaker, which the Ukraine clinched with a delicate backhand drop volley.
His confidence up and producing the type of sublime attacking tennis he delivered to stun Roger Federer at Wimbledon last year, Stakhovsky controlled the second set and stood within two games of the final.
But Tomic dug deep to break the world No.101 in the 11th game and snatch the set on his fourth set point to send the match into a decider.
Looking fatigued, Tomic called for the trainer before the start of the third set but fired up again to claim the decisive break in the seventh game with a lunging forehand cross-court pass.
He broke the Ukrainian again in the ninth game to seal victory after two hours and 13 minutes.
He will be bidding to become the first Australian to successfully defending his crown in Sydney since Lleyton Hewitt in 2005.
Hewitt also claimed back-to-back titles in 2000-01.
Tursunov won the Sydney title in 2008, but Del Potro broke him three times to power past the world No.32 in just 64 minutes.
The former US Open champion sent down nine aces in nine service games en route to the 25th final of his career.
Del Potro launches his Australian Open campaign against a qualifier next week and, regardless of Saturday's result, will head to Melbourne Park with plenty of confidence.