Ahead 14-7 at half-time, the Kiwis ran in four second-half tries to seal the win.
Tim Mikkelson, Vilimoni Koroi and Joe Webber scored for the All Blacks Sevens who rallied from 12-7 down at halftime.
In a repeat of last year's Cape Town semi-final - in which the hosts knocked the Kiwis out to secure their final spot against England - the New Zealanders celebrated a win this time around after also beating the defending Cape Town title-holders, England, in a quarter-final clash earlier in the day.
New Zealand haven't won a men's title since March 2016, when they defeated South Africa in the final of the Vancouver Sevens.
Despite a shock 22-0 loss against the U.S. in their opening game of the weekend‚ NZ powered their way through to the final where they beat Argentina 38-14 in a disappointingly one-sided match.
A late try by NZ's Joe Webber, their third of the match, was enough to see them over the line in a contest where they also survived a yellow card against Joe Ravouvou.
However, closing tries to Koroi and Sione Molia sealed the match comfortably for New Zealand.
Star wing Seabelo Senatla was both villain and hero against Fiji the day after he became the fastest man to 200 tries in Series history‚ achieving the feat in his 35th tournament.
Australia fought back early in the second period with tries to Simon Kennewell and Lewis Holland reducing the deficit to 21-12 but that was as close as they got. Conversion: Branco du Preez (1). Conversions: Koroi, Andrew Knewstubb.