With the World Cup looming in June, the rivals will meet in front of a sell-out crowd in Wellington on Wednesday, followed by games in Auckland on Friday and Sunday.
New Zealand triumphed in their last meeting in the shortest format, by 89 runs in October 2022 in Sydney at the World Cup, but Australia have since lifted the 50-over World Cup and are coming off a 2-1 T20 series win over the West Indies.
"We're probably underdogs but we are used to that tag and don't think much of it," Santner told reporters.
"It's always a pretty cool time when the Aussies come over. You always want to challenge yourself against the best in the world, and they're up there for sure."
The Black Caps and Australia last met in a T20 series three years ago, with hosts New Zealand winning 3-2.
"It's special," Santner said. "We probably don't play Australia as much as we probably should, but the trans-Tasman clash is always good fun."
"Looking at their squad at the moment, they're a very, very good team with all bases covered," added the all-rounder.
"We’ve just got to do our thing, we've got our plans in place."
The tourists, captained by Mitchell Marsh, are at full-strength.
David Warner, who recently retired from Test cricket, is 54 runs away from overtaking former captain Aaron Finch as Australia's all-time leading scorer in men's T20s.
New Zealand have rested world-class batsman Kane Williamson but added experienced seamer Trent Boult to their attack.
"We know how good they're going to be and how explosive their team is," Santner said of the Australians.
"So for us it's just about staying in for as long as we can and see what happens.
"We want to put up a good fight this series, then we can look forward after that."
The T20 series is followed by two Tests.
