The ACT is the only jurisdiction to have supported a Voice to Parliament so far, with just over half of its votes counted.
The tally was still in its early stages when the ABC's election analyst Antony Green called the ACT as a "yes" vote just before 7pm, noting its results would not count towards the majority of states.
Mr Green has called "no" votes for NSW, Tasmania, South Australia and Queensland as well as the majority vote, and predicted the referendum would be defeated.
By 8.30pm, it was clear the ACT had overwhelmingly voted in support of altering the constitution to recognise the First Peoples of Australia by establishing an Aboriginal and Torres Strait Islander Voice.
Canberra had supported a "yes" vote, 63.52 per cent to 36.48 per cent, with 164,026 votes counted of 316,837 enrolled.
"While the voters count towards a national total, the ACT does not count towards the majority of states question," Mr Green said early in the evening, referring to the double majority needed for a successful referendum.
"We believe the ACT has voted 'yes' to the Voice, but as I said, that doesn't factor into the equation with states for determining the referendum result."
Canberra voters flowed through the halls of Old Parliament House on Saturday, opting for a historic setting to cast their votes in the Voice referendum.
The Canberra institution had already received large numbers of voters pre-polling in the lead-up to the referendum.
The ballot paper asked voters to decide whether to alter the Constitution to recognise the First Peoples of Australia by establishing an Indigenous advisory body to Parliament.
"Pre-polling has been huge actually, we've been extremely busy all week," the Museum of Australian Democracy's Nanette Louchart-Fletcher said on Saturday morning.
"Today I think is more about our interstate voters, so we've got a bit of a line for our interstate voters at the moment, locals are flowing through quite quickly."
Speaking to journalists from Old Parliament House on Saturday, Australian Electoral Commissioner Tom Rogers said more than 6 million Australians had pre-polled.
Polling booths closed at 6pm on Saturday, when tallying got under way.
Ms Louchart-Fletcher said it had been "a great hive of activity" on Saturday morning, as the polling booth opened and a sausage sizzle got underway.
"I would say there is no better place to vote in Australia than Old Parliament House," she said.
"This is where history happened, a lot of the decisions that impact all of our lives were made in this building so it's a very special place to vote.
"This year we're voting in Kings Hall as well, right in the epicentre where our politicians would stride back and forth so it's really special."
Fred, 73, and Judith Barnes, 68, enjoyed a democracy sausage on the steps outside after voting "yes" for a Voice to Parliament.
"I think it's long overdue," Mr Barnes said.
Ms Barnes added: "Yes I think it is overdue and if not now, when?"
"I just really, in fact, I worry about waking up tomorrow if 'no' gets up ... we don't have a leg to stand on in future if we want to criticise countries that are mean to their minority groups cause we're mean to our own."
Chief Minister Andrew Barr arrived later in the morning to enjoy a democracy sausage, sporting a "yes" hoodie, while Opposition Leader Elizabeth Lee donned her "Liberals for Yes" shirt on arrival.
"We know that it's been a bit concerning seeing some of the polls across the country but let's hope that ACT pulls through for 'yes'," she said.
Asked why she was supporting the Voice to Parliament, the Liberal MLA said it was about recognition, listening to the community and taking action to close the gap.
"And it's a simple and constitutionally elegant way of doing [that]," she said.
"So it was something that I thought about quite deeply for a long time and realised that it was something I could get behind."
She had brought her two children along, as she handed out how-to-vote cards.
"It was a little bit hard getting out of the house with both kids today, but if they can witness the festival of democracy in action I think that's a good thing," she said.
Scarlett Fittler, 18, arrived at Old Parliament House to vote for the first time, with her father Derek Fittler.
She planned to "emphatically vote 'yes'", and said she felt the weight of responsibility on her shoulders but was excited to cast her vote.
Her father agreed, saying: "I would love to see this get up. I think this a long time overdue to have recognition in the Constitution and from my own perspectives I see the Voice as an opportunity to have a different discussion and engagement with Indigenous culture."
