Anyone travelling to the ACT from a COVID-19 hotspot in NSW will now require an exemption.
People from Sydney's northern beaches, Greater Sydney, the Central Coast and Wollongong will not be legally permitted to enter the ACT without a valid pass.
The updated health direction will come into effect from midday on Saturday and any non-compliance will result in penalties, the ACT government says.
It comes after NSW on Friday reported three new coronavirus community transmissions, all linked to western Sydney.
Any travellers from these regions into the ACT for "extraordinary circumstances" are required to apply for an exemption at least three days prior to the planned entry but no more than 14 days ahead of time.
These changes do not affect current restrictions for ACT residents returning from COVID-19-declared areas, whereby until at least January 6 authorities must be notified followed by a mandatory quarantine for 14 days.
ACT Chief Health Officer Kerryn Coleman said the travel restrictions were tightened to protect the state's health.
"In recent days we have continued to see around 80 non-ACT residents from COVID-19 affected areas of NSW travel to the ACT daily," Dr Coleman said in a statement on Saturday.
"As a result we now have around 2000 people in quarantine in the ACT, 25 per cent of which are non-ACT residents."
"For those in COVID-19 affected areas of NSW, we ask that you respect the public health direction that has been put in place and do not travel to the ACT."
Canberrans have also been reminded not to travel to Greater Sydney, or any other COVID-19 affected areas, and to reconsider travel to NSW more broadly.
Police officers will patrol the Federal Highway to enforce the new rules.
© AAP 2021