Border security patrols will be ramped up and Christmas Island reopened in response to new laws fast-tracking medical evacuations for asylum seekers.
Prime Minister Scott Morrison says Christmas Island's detention centre will deal with any potential new boat arrivals and medical transfers from Manus Island and Nauru.
But Christmas Island's local council warned its small regional hospital is not set up to handle asylum seekers with complex medical needs, if people are transferred to it.
The controversial laws passed the Senate 36 votes to 34 on Wednesday, in a humiliating defeat for the coalition a day after suffering a historic loss in the lower house.
The laws, which only apply to around 1000 asylum seekers currently on Manus Island and Nauru, give doctors more say in recommending medical transfers to Australia.
"I'm standing between people smugglers and bringing a boat to Australia," Mr Morrison told reporters in Canberra on Wednesday, pledging to scrap the laws if re-elected.
"My job now is to ensure that the boats don't come."
Earlier, Opposition Leader Bill Shorten sent his own message to would-be asylum seekers.
"The legislation applies for people who are already there (on Manus and Nauru) - it does not apply to anyone new," he told reporters.
"If you think that by buying a ticket on an unsafe boat, paying a people smuggler, a criminal syndicate, you'll get a better deal to come to Australia, you're wrong."
The government says the Christmas Island re-start will cost about $1.4 billion over four years.
New Zealand Justice Minister Andrew Little told reporters in Wellington the decision to reopen Christmas Island was disappointing.
"The conditions aren't satisfactory," he said.
Christmas Island local council chief executive David Price said the local hospital was so small it made more sense to send sick asylum seekers straight to the mainland.
"If a person has a compound fracture they're air-vacced out. There's no operations done (here)," Mr Price told ABC Radio in Perth.
"Some of these people would have serious mental problems that need to be dealt with by specialists. We haven't got the specialists here to do that."
The laws passed the Senate on Wednesday and will be given royal assent.
"This is the toughest decision I've had to make since I came into this chamber," Senator Derryn Hinch said as he delivered his crucial vote on the laws.
Government Senate leader Mathias Cormann said the changes would mean "rapists, murderers and pedophiles" will be allowed into the country.
Under the new laws, the home affairs minister can reject medical transfers if the person poses a threat to the Australian community.