The All Blacks have cruised to a Bledisloe Cup clean sweep in Japan, dismissing Australia 37-20 in the third test in Yokohama.
Tries to flanker Liam Squire and skipper Kieran Read gave the All Blacks a 17-10 halftime lead, with Barrett's kicking radar on song in sinking both conversions and a penalty.
But the Wallabies ended the first half on a high note when winger Sefa Naivalu dived over out wide right on the stroke of halftime, No.10 Bernard Foley equally accurate with the boot in nailing a difficult conversion.
The two teams traded penalties early in the second spell, but momentum shifted in the All Blacks favour when Barrett split the Wallabies defence open as the hour mark approached.
He struck from 40 metres out after Rieko Ioane made the initial break from a scrum before offloading for Barrett to let fly.
Replacement Wallabies hooker Tolu Latu was sinbinned for retaliation with 14 minutes remaining, and the All Blacks took advantage almost immediately, Ben Smith grabbing an intercept try after pouncing on a loose Israel Folau pass.
Folau grabbed a consolation try for Australia with just four minutes left on the clock, but man-of-the-match Ioane completed the scoring with the All Blacks' fifth five-pointer three minutes before fulltime.
The Wallabies, with plenty to prove, exploded out of the blocks in front of 46,143 fans in Yokohama and almost scored in the second minute only for fullback Dane Haylett-Petty's effort to be ruled out by the TMO.
After that, New Zealand took control, dominating possession and territory throughout the first half.
Australia looked dangerous with ball in hand but were plagued by errors, turning the ball over six times in the first half to New Zealand's one and, as usual, the world champions made them pay.
Captain Kieran Read said the all Blacks strong start had played a key role in the win.
"I felt we were really able to control the game," he told Sky Sport.
"You've got to read what the game presents, and the scoreboard went our way early so we just wanted to try and maintain that little bit of a buffer and really make them chase the game.
"Our defence was really good tonight, so once we got in front and they tried to play their way out, we managed to keep them at bay."