The Argentine world number five took just 53 minutes to master the Australian defending champion 6-3, 6-1.
It was del Potro's 18th career title and he became the first Argentine to win in Sydney since David Nalbandian in 2009.
It was the ideal lead in to Monday's Australian Open for del Potro, who plays a qualifier in the first round and is seeded to face world number one Rafael Nadal in the quarter-finals.
"Finals are never easy, but I was surprised at my level of play tonight. I think I played great," del Potro said.
"My forehand was perfect. I made a lot of winners, many aces, good slices."
The big Argentine served eight aces and broke Tomic's serve four times for a comprehensive win.
"To start the year in this way it's very positive looking forward for the rest of the season. I need to keep working in the same conditions and the same way.
"Now it's the hardest tournament for us, and I will see if I can go further than last year (third round) in Melbourne.
"After two or three matches I started to play much better. My movement was faster than in the first rounds here."
It was del Potro's second win over the 52nd-ranked Tomic, who was defending his title after beating South African Kevin Anderson in last year's final.
"I think Bernard was a little frustrated after seeing me very focused on the match and hitting the ball so well," the Argentine said.
"He is still young, but he has everything to win titles, and he will reach more finals very soon."
Tomic has only a few days to recover mentally for his daunting first round encounter with Nadal at the Australian Open on Tuesday.
"It's a good opportunity. I'm playing a legend, probably one of the best players we have around now. He's a champion, won that many Grand Slams," Tomic said.
"It's not easy. He's one of the most difficult players to play. Unfortunately I have to play him first round. I'm going to bring it to him. I'm going to prepare as best I can to play him."
Del Potro dominated the final, breaking the 21-year-old Australian in the seventh and ninth games of the first set.
He dictated the play from the baseline and his booming forehands gave Tomic no chance as he broke the Australian twice more in the fourth and sixth games of the second set.
He sealed his victory with an ace.
"Tonight Juan showed why he's such a quality player," Tomic said.
"So there was nothing I could have done. I tried to keep up, but he kept playing the way he was playing. I haven't seen a guy play a second set like that. It was too good."