Police arrested a man this afternoon and charged him with threatening to kill.
It was yet to be decided when he would appear in court.
Update: The branch would remain closed to the public for the remainder of this afternoon but ACC staff were still hard at work at their desks, senior media advisor Stephanie Melville said.
The Child, Youth and Family office next door was also closed.
Earlier: Tauranga ACC is in lockdown following a threat to the Grey St branch this afternoon.
The office has closed its doors to public after a man contacted ACC staff and threatened staff about 1.30pm.
A police spokeswoman said they received a call from ACC staff following the threat and police were making inquiries, along with staff from ACC, to identify the person or persons responsible.
The spokeswoman would not elaborate on the nature of the threat but said it was understood the office been shut down.
ACC senior media advisor Stephanie Melville confirmed there had been a phone threat made.
"The police are investigating a phone threat and our staff did exactly the right thing, they followed protocol, let the police know, police are investigating and the office is closed while that is being seen to by police."
When asked whether the Tauranga branch was the only branch affected, she said it appeared to be so but because staff were in lockdown, she could not contact them to confirm.
Police were meeting with the client who made the threat and would advise staff of when it was safe to reopen.