New Zealand went out to an early 17-3 lead after tries to Harry Plummer and Devon Flanders within the opening 12 minutes before Australia struck back with tries late in the first half.
Plummer opened the scoring in just the fifth minute after going on his own close to the line, barging through the Australian defense. He converted his own try.
Hawke's Bay number eight Flanders then extended the lead seven minutes later with a 70m intercept run shortly after Australia failed to convert their own intercept chance.
Plummer added the conversion followed by a penalty in the 17th minute to make it 17-3 as another dominant New Zealand performance looked on the cards.
However Australia crossed over through flanker Fraser McReight in the left-hand corner before New Zealand gave away a penalty try shortly before the break.
The infringement also saw Tevita Mafile'o yellow carded for coming through a wheeling scrum and kicking the ball close to the line.
Both teams shared penalties early in the second half before a Vilimoni Koroi run from halfway set-up Jamie Spowart for a try midway through the second half.
New Zealand advance to the semifinals having scored 19 tries and conceded just three during pool play.
