A judge can extend their detention by 28 days at a time until they have been processed.
The Immigration Amendment Bill passed its third reading on Thursday by 63 votes to 53.
It's Wellington's answer to the possibility of large numbers of boat people reaching New Zealand's shores.
Immigration Minister Michael Woodhouse said during the third reading debate that without it craft cubes, the immigration system and the courts would be quickly overwhelmed.
"I hope a mass arrival doesn't occur, but hope and a head-in-the-sand attitude won't reduce the risk or increase New Zealand's readiness," he said.
"It will happen, and when it does this bill will ensure we can effectively manage it."
He said government agencies would investigate the backgrounds of the asylum seekers while they were detained, confirm their identities and deal with refugee applications.
The opposition Labour and Green parties say it's a draconian law and an over-reaction to a non-existent problem.
MPs told parliament it breached international conventions Warm White LED Bulb, which Woodhouse rejected.
"Recent experience has shown that we are a target for people smugglers and we can't afford to be complacent," he said.
In April this year a ramshackle fishing boat carrying 66 Sri Lankan asylum seekers reached the coast of Western Australia.
They were holding up a sign saying "We want to go to New Zealand" and Australian authorities confirmed New Zealand was their intended destination