Hewitt, bidding to recapture the title he lifted in 2011, reeled off six consecutive points in the third set tie-break after world number 15 Raonic seized a 3-0 lead.
The 31-year-old former World No 1 sealed victory on his second opportunity after Raonic had saved a match point with an ace. Hewitt will be playing in a record 17th straight Australian Open when the first major of the season starts. Meanwhile, Argentine Juan Martin del Potro beat Frenchman Paul-Henri Mathieu 6-4, 3-6, 7-6 (7-3).
Photos: Huma Qureshi, Neha Dhupia and other celebs at MAMI
Flashback: When sexy models sizzled in bikinis at Tokyo fashion show
Photos: Amy Jackson, Daisy Shah at Mumbai airport
Photos: Sridevi, Irrfan and other celebs at 'Mughal-e-Azam' screening
Photos: WWE Diva Kelly Kelly sizzles in bikinis on Instagram