A source was identified for 40 of Friday's infections. More than half were in household contacts of existing cases.
At least 31 spent part of their infectious period in the community.
Another 17 were in quarantine the whole time.
ACT Chief Health Officer Kerryn Coleman said the daily tally is the highest of the current outbreak.
"I know that today's case numbers will be concerning for some people given this is the highest daily number in the outbreak so far," Dr Coleman said.
"And I must admit, it is a little concerning for us as well."
The previous daily case high was 32.
Chief Minister Andrew Barr and health officials are concerned about the daily case rise while the territory remains in lockdown, albeit with progressively easing restrictions.
"Today's increase in case numbers will come as a shock to many but it's an important reminder that the virus is still very much active in our community," Mr Barr told reporters.
"When we get to higher vaccination rates and we start to further reduce our public health safety measures, daily case numbers like this will become the norm. But we're not at that point yet."
The chief minister is worried 40 per cent of eligible residents are yet to be fully vaccinated.
Canberra has become the first jurisdiction to reach a 90 per cent first dose rate for people aged 12 and older.
By the end of October, Mr Barr expects 90 per cent to be fully vaccinated.