After a convincing win in Auckland earlier this week, New Zealand won the toss and chose to bat in today's match.
Guptill was next to go for 31 and the wickets steadily tumbled, with Kane Williamson's 60 the highest total of any Black Cap.
Australia quickly went about their business in reply, with Usman Khawaja and Warner putting on 122 for the first wicket before Khawaja was caught and bowled by Santner.
The wickets of danger-men Steven Smith (2), George Bailey (0) and Glenn Maxwell (6) all fell in the space of three overs to give New Zealand a lift, but Warner's 98 and a seventh-wicket partnership of 86 from unbeaten duo Mitchell Marsh (69) and John Hastings (48) saw the Aussies reach their target with three-and-a-half overs to spare.
The deciding match of the series takes place in Hamilton on Monday.