Victoria and NSW are welcoming their first quarantine-free international arrivals since Australia's border snapped shut last year.
Home Affairs Minister Karen Andrews is confident Australia will be able to keep its international border open because of COVID-19 vaccination rates.
Slightly more than 77 per cent of Australians aged 16 and older are double-dosed, while about 88 per cent have had one dose.
"Australia is open for business, people can reunite overseas with their families, start to travel again, so today is an enormously significant day," she told the Seven Network on Monday.
Treasurer Josh Frydenberg declared the lifting of international travel restrictions and the opening up of travel between NSW, Victoria and the ACT good news for the country's economy.
"It's a day for celebration, the fact that Australians can move more freely in and out of our country without home quarantine, if they're double-vaccinated," he told ABC TV.
"We've seen an additional $150 million a day being spent across NSW and Victoria since the restrictions have eased, and we've also seen ticket sales for airline travel going gangbusters."
It comes as people Queensland and Western Australia are urged not to be complacent about getting the jab.
Queensland has fully vaccinated 64 per cent of its over-16 population and Western Australia, 63 per cent.
Infectious disease expert Nick Coatsworth, a former deputy chief medical officer, urged people not to wait to to protect themselves.
"It's really worrying for me because there are people who are no longer with us in NSW and Victoria that didn't have that sense of urgency," he told the Nine Network.
"It does seem to be the case COVID has to hit your community before the vaccine rates increase."
Meanwhile, a quarantine-free travel bubble between New Zealand and Australia has been given the green light to resume.
A similar travel bubble is set to open between Singapore and Australia later this month.
NSW reported 135 new local COVID-19 cases on Monday alongside four additional deaths.
Victoria recorded 1036 cases and 12 more deaths on Sunday and the ACT seven new cases.