The Lyttelton Port Company has determined all of its staff will need to be vaccinated.
CEO Roger Gray told the Herald the decision was made after a risk assessment process and subsequent consultation with staff.
He said they are working with about 20 employees who remain unvaccinated, out of about 650.
A timeline for when staff must be vaccinated by has yet to be set and discussions on final options have just begun.
The port is also looking to implement regular testing for all staff, not just border-facing ones.
Visitors to the port corporate offices are also required to provide an additional form of ID at the front gate.
"We now require all visitors to provide their Covid-19 vaccine passport upon entry."
At this time, we are working with about 20 employees who remain unvaccinated, in our workforce of about 650.
It comes after the announcement earlier this month that all unvaccinated staff at the port would be stood down on full pay while a risk assessment is carried out.