The tone was set in just the second minute of the game when Australian second-rower Louis Geraghty fell over the try line from close range. It wasn't the only try the visitors scored from close range as they looked to ease through the Kiwis' defence every time they got within 10 metres of the try line - and missing 43 tackles, 18 more than the Australians, and committing more errors didn't help the cause for the hosts.
The Kiwis took a brief lead midway through the first half, but they never looked convincingly on top of the match.
The second half was telling, when North Queensland Cowboys up-and-comer Enari Tuala went over in the corner five minutes after the break.
Stamping their authority on the scoreboard, the visitors refused to slam the door on their hosts. A number of handling errors inside their own 40 invited pressure from the Junior Kiwis.
Winger Steven Marsters made them pay after a deft bomb from five-eighth Dean Blore fell into his hands.
Down by 10 with the time on the clock in single figures, the Junior Kiwis couldn't mount a game-winning charge late in the piece. Instead, Tuala slammed the door shut in the 78th minute, crossing the stripe for his side's seventh try of the afternoon to seal the win.
Junior Kangaroos 40 (Tino Fa'asuamaleaui 2, Enari Tuala 2, Louis Geraghty, Thomas Flegler, Corey Allan tries; Zac Lomax 6 cons)
Junior Kiwis 24 (Sean Mullany, Isaiah Papali'i, Jackson Ferris, Joseph Vuna, Steven Marsters tries; Chanel Harris-Tavita 2 cons)