You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
The Black Caps extended their lead to 2-0 in the five-match series after thrashing the visitors by 53 runs in Christchurch earlier this week.
Opener Guptill smashed 97 off 50 balls as New Zealand put 219 for seven on the board to set an imposing chase at the University Oval.
He combined with skipper Kane Williamson for a 131-run partnership for the second wicket after Tim Seifert was dismissed early for three.
Williamson made 53 off 35 balls before being bowled by Adam Zampa at the end of the 16th over, leaving Jimmy Neesham to steer the innings to a close.
The all-rounder faced just 16 balls, but hit six sixes in his 45-run innings to see the Black Caps through to 219-7.
New Zealand's bowlers reduced Australia to 113 for six with the wicket of Mitchell Marsh in the 13th over but Marcus Stoinis and Daniel Sams combined to keep the tourists in the game with a swashbuckling 92-run partnership.
Australia needed 15 runs off the last over, but Neesham had Sams caught for 41 in front of the deep midwicket boundary with the first ball.
Stoinis needed a six and a four to win the game on the last two balls but slogged Neesham high into the air on the first delivery to be caught at long-on for 78 as Australia finished 215 for eight.
The best bowling figures for the Kiwis came from Mitchell Santner.
His 4-31 off 10 overs included three wickets in four balls, as he dispatched Josh Phillipe for 45, then Ashton Agar and Mitchell Marsh without scoring.
The third T20 is in Wellington next Wednesday.
- Reuters and RNZ