The top seeded Sugiyama, who also beat Petrova in the final at Linz last October, looked to be in all sorts of trouble after dropping the first set.
But the lightly-built world number 10 regained her composure to run away with the final two sets and capture her sixth career title while denying the hard-hitting Russian her first.
Seeded second, the 21-year-old Petrova's hopes of winning evaporated when she strained a thigh late in the second set.
She received treatment for about an hour after the match then announced she was pulling out of next week's Canberra Classic, where she was the top seed.
"I just kept my concentration. I don't know how it happened but I am so happy," said Sugiyama, who also won the event in 1998.
"My movement wasn't there. It's just a mental thing. I never gave up. I just played every single point and tried to be aggressive.
"She has never won a title so I was sure she would get nervous and it would be tough to close out the match," Sugiyama added.
