The Apple Isle, which is currently coronavirus-free, was set to open its border to SA, WA and NT on August 7, followed by Queensland, NSW and the ACT on August 14.
However, Tasmanian Premier Peter Gutwein on August 3 said his government would not open the state to anyone until at least August 31.
Health authorities would review figures on the mainland on a week-by-week basis.
It comes as Victoria declares a state of disaster and imposes a 8pm-5am curfew in Melbourne, with hundreds of new COVID-19 cases recorded each day.
“It simply isn’t the time to open the borders right now,” Gutwein said.
“Now is the time to utilise our best asset, which is our moat.”
Tasmania recorded no COVID-19 cases from about 800 tests on Sunday.
The Tasmanian government’s decision to continue mandatory 14-day hotel quarantine periods for arrivals follows a decision on Friday to ban travellers from COVID-19 hotspots in Queensland, with virus-hit regions of NSW and Victoria already banned.
People from those areas are only allowed in under exceptional circumstances.
Gutwein implored people to do the right thing when filling out border documents.
Tasmania regained its virus-free status after the recovery of a young woman who returned from Victoria and tested positive while in hotel quarantine on July 20.
Some business groups had called for borders to stay closed and internal restrictions to be further eased, considering the island state is virus-free.