Queensland will close its border to all of New South Wales and the ACT from 1:00am on Saturday.
It comes as the state recorded one new case of coronavirus overnight.
The 68-year-old Queensland woman was diagnosed with the virus in the past 24 hours and authorities are still investigating the source of the infection.
Two historic cases have also been added to the state’s total of 1,088 cases.
The hotspot declaration means anyone travelling from NSW or the nation’s capital will soon be banned from entering the Sunshine State.
Queenslanders who return after travelling there will be sent to mandatory hotel quarantine for 14 days at their own expense.
Premier Annastacia Palaszczuk said she was increasingly concerned about community transmission rates in southern states.
“We cannot risk a second wave. We have to act decisively,” she said.
“We have to put Queenslanders first.”
The move means New South Wales and the ACT will join Victoria on Queensland’s list of declared coronavirus hotspots.
Ms Palaszczuk said her decision was influenced by a number of people who had breached the state’s border requirements, by lying to authorities about their whereabouts.
“This is the right decision for Queensland,” she said.
“We cannot put Queenslanders at risk — it is too important.”