Hewitt only lost one point on serve in the first set, made just three unforced errors and secured it on his fifth set point in 27 minutes.
Hewitt faced break point in the fifth game of the second set but saved it with a lunging, angled backhand volley and held for a 3-2 lead.
Federer, who is ranked No. 6 and didn't win a major last season as he experimented with a new racket, fended off a breakpoint to hold at 4-4 in the second set and then rallied from 40-love to break Hewitt in the next game. He took the second set with three aces and a rifling inside-out forehand winner.
Hewitt fended off four break opportunities in the opening game of the third set that lasted more than 10 minutes, and again faced break points in his next service game.
But just when Federer seemed to getting the upper hand, Hewitt broke for a 3-1 lead. Federer made a misjudgment when he left one of Hewitt's groundstrokes at 15-15 that landed well inside the baseline and the momentum turned from there.
A raucous section of the stadium, dressed in canary yellow singlets and calling themselves the Fanatics, were chanting and singing for Hewitt throughout the match, drowning out the support for Federer, who is usually a favorite with Australian crowds.
