The visitor chased down its 278 target with 10 balls to spare, inflicting the first one-day defeat on Australia in 10 games, although this was not counted as a full international.
The best bowler for the host with ball in hand was spearhead Mitchell Starc, whose three-month layoff came to an end in encouraging fashion.
Starc bowled at high pace and took two wickets with trademark yorkers, finishing with 2-14 from five overs before he was withdrawn from the action midway through New Zealand’s run chase, which saw just three wickets fall and 47.2 of the allotted 50 overs required.
The left-arm quick was joined in the attack by new World Cup addition Kane Richardson (0-52), Australia A quicks Sean Abbott (0-57) and Michael Neser (0-62), and spinners Nathan Lyon (0-54) and Glenn Maxwell (0-39), all of whom failed to make any inroads.
After David Warner (0) and Aaron Finch (16) fell to Kiwi seamer Doug Bracewell, who bowled an excellent new-ball spell, Usman Khawaja put together a composed 56 to do his World Cup hopes no harm and extricate Australia from a less-than-promising position early in their innings.
Khawaja and Shaun Marsh (28) could well be competing for the No.3 spot in Australia’s first-choice XI, and the two unfurled some typically impressive stroke-play, particularly through the cover region as they looked set for long stays in the middle. But Marsh was again caught slashing outside off stump and Khawaja found himself the victim of an outstanding catch from Jimmy Neesham, who intercepted a full-blooded pull shot at short mid-wicket.
It set the scene for Smith and Maxwell, who combined the classical with the unorthodox as only they can.
After spending some one-on-one time in the nets with coach Justin Langer before play, Smith hit the ground running when he entered the action from the unfamiliar No.5 position. He moved from three to seven with a beautifully struck straight drive and an over later cover drove leg-spinner Todd Astle for six to really move into his stride.
In no time he and Maxwell added impetus to an innings that had been hitherto chugging along at a gentle pace.
Brief scores: New Zealand XI 283/3 (Will Young 130) beat Australian XI 277/6 (Smith 89*, Khawaja 56, Maxwell 52) by seven wickets
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