The Northern Irishman edged ahead of Welsh rival Chaz Davies on the last of the 22 laps to clinch his third successive win in Australia.
Rea's British and Kawasaki team-mate, Englishman Tom Sykes, was third.
"It was a little bit like a bicycle race and no-one wanted to put their nose in front," Rea, 30, said.
The champion's victory - his 39th in WSB - ended Davies' six-race winning streak from 2016.
Rea is one of four riders to clinch back-to-back Superbike titles but is aiming to become the first to win three in a row.
He still lies two titles behind Carl Fogarty's record of four championship successes.
Toomebridge man Eugene Laverty, who is back in the series after two campaigns in the MotoGP paddock, finished eighth on his Milwaukee Aprilia.
There will be a second Superbike race at Phillip Island on Sunday.
Defending world champion Jonathan Rea has won the opening race of the 2017 Superbike World Championship at Phillip Island.