Johnson fired a five-under 68 on another blustery day at the Kapalua Resort to finish four shots clear of defending champion Steve Stricker (69).
With the win, Johnson becomes the first player since Tiger Woods to win at least one tournament in six consecutive years straight out of college.
Johnson posted a 16-under 203 total at the weather-hit event that was trimmed to three rounds and forced to a rare Tuesday finish because of relentless howling winds that did not allow the first round to be played until Monday.
Stricker got to within a shot of his U.S. Ryder Cup team mate with five holes to play but could not keep up the rally as Johnson went on to collect his seventh career win.
American Brandt Snedeker, last season's FedExCup champion, had a solid start to his 2013 campaign, also closing with a 69, to finish alone in third, six shots back of Johnson.
Masters champion Bubba Watson (71) was a further shot back in a tie for fourth with fellow American Keegan Bradley (70). (Reporting by Steve Keating in Toronto; Editing by Frank Pingue)