Players from both teams huddled together in the middle of the field to lead a moment's silence for the 50 people killed in last month's massacre when a white supremacist gunman stormed two mosques in the quiet southern city.
A determined New Zealand set the early pace before Australian co-captain Nick Malouf slipped straight down the middle and sprinted across the try line from 30 metres out, levelling the scoreboard at 14-all.
But New Zealand pulled ahead again when Joe Ravouvou broke through and jogged the ball over shortly before half time.
Joe Webber, returning from injury this week after a reactive arthritis diagnosis last year, made the sixth try of the match.
"It's obviously been a tough time for New Zealand," coach Clark Laidlaw told reporters ahead of the tournament.
"Certainly we're aware that we're the first national team to play since the event ... the best thing we can do for Christchurch and for our country is to play bloody well."
Elsewhere in the pool matches, the US Eagles made short work of Spain at 36-7, while a rowdy Fijian crowd in the north stand cheered a 22-5 victory for the reigning Hong Kong champions over Kenya.
Fiji are chasing their fifth consecutive victory in the tournament.
Brazil secured a return to the women's series after a two-year hiatus with their 28-19 qualifying finals victory over Scotland.
"We worked really, really hard for this," said vice-captain Isadora Cerullo.
"We're looking to build even more, bring in a lot of new players and show everyone ... that we deserve to be back on the world circuit."