Going into the last stage, 2006 and 2011 winner Gerrans held a one-second lead over 2011 Tour de France-winner Evans and was five seconds ahead of Italian Diego Ulissi.
The overall standings for the top three remained unchanged after the sixth and final stage of the race in and around Adelaide.
Winning the title with his Australian team Orica-GreenEDGE on the country’s national day made it a special occasion for the 33-year-old rider.
“I’ve got my third Tour Down Under win thanks to an outstanding team,” a jubilant Gerrans told reporters.
“This is an Australian team, on Australia Day, in a WorldTour event, what else could I ask for?”
Evans and Ulissi both needed time bonuses to wrest the lead from Gerrans but a three-man breakaway took the extra seconds available at two intermediate sprints during the 85.5km stage.
Orica-GreenEDGE controlled the race superbly as Gerrans pointed out after his victory.
“It’s been a hard race for me and my team mates,” Gerrans said. “It’s been difficult to get the Ochre jersey back, what a tough week.
“I was confident in my team mates to take me home safely, which they did today. Until I crossed the line, I suspected that Diego Ulissi would try and do something, but it went all right.”
Evans was happy with his start to the year.
“I took my best judgement on the road (so) I have to be satisfied with how it went,” Evans, who rides for the BMC Racing team, said.
“We prefer to win, that’s what we’re hard-wired to win. (But) to lose by one second shows that we’re in a good way.”
(Writing by Sudipto Ganguly; Editing by John O’Brien)