From Thursday, people aged 18 and over will only need to wait three months from their second COVID-19 vaccination to get their third.
The interval reduction from four to three months was previously scheduled to come into effect on January 31.
NSW, Victoria and South Australia all made similar moves to lessen the interval on Wednesday.
ACT Chief Minister Andrew Barr said the take-up rate for booster shots in Canberra had been strong.
"Just like the initial vaccine rollout, the ACT is leading the way with booster doses, with one-in-three Canberrans aged 18 and over now having received a third vaccination," Mr Barr said.
The decision means an extra 183,000 Canberrans will be eligible for the COVID-19 booster.
A second mass vaccination clinic, set up at Canberra Airport, will begin operating next week to accommodate the wider eligibility for boosters.
It will run in addition to the mass clinic operating at the Australian Institute of Sport.
As many as 32,500 booster doses will be able to be administered in the ACT each week in government-run clinics.
The Canberra Airport site will prioritise boosters for school and early childhood staff.
It comes as hospitalisations from COVID-19 fell in the ACT in the past day, while infections also decreased.
The latest figures showed 1467 cases were recorded on Wednesday, with 654 of those from PCR tests and 813 from rapid antigen tests.
The number of new cases was slightly down from the one-day high of 1860 infections reported on Tuesday.
The number of COVID-19 patients in hospital dropped from 63 to 60 in the past day.
The number of patients with the virus in intensive care has also fallen, from six to five, while the number of patients on on a ventilator remains at two.
ACT Health Minister Rachel Stephen-Smith said earlier in January modelling had shown the peak of hospitalisations from COVID would be about 60 patients.
The number in intensive care was also forecast to reach as high as seven to 10 at one time.
Health authorities also revealed more than 34 per cent of children aged between five and 11 have received their first dose since the child vaccine rollout began last week.
14°C