Auckland Transport says authorities - rather than its own staff - will have to enforce the requirement for passengers to wear masks from midnight tonight.
It is mandatory for anyone who is using public transport anywhere in the country to wear a face covering from midnight tonight, if people do not have a mask they can use a scarf or bandana.
People with a disability or physical or mental health condition that makes covering their face unsuitable are exempt, as are those aged under 12.
Health Minister Chris Hipkins has said there will be a "light touch" in terms of enforcement although people can face a $300 infringement notice or a fine of up to a $1000 imposed by the courts.
Auckland Transport spokesperson Mark Hannan said they are hoping to take an educational approach rather than trying to strictly enforce the new rule.
He said many Aucklanders already wear face coverings, so the transport operator is hoping for a smooth transition.
"I think it's becoming quite normal now for people in Auckland to wear face coverings, if you go into a supermarket here just say, or on public transport, you will find that most people are wearing some sort of face covering."
Auckland Transport's drivers will also be wearing masks and buses will be run with about half their full passenger loads to help maintain physical distancing.
Anyone attending court in the Auckland region will also be required to wear a mask in public spaces and courtrooms from tomorrow.
The Chief Justice said the step is necessary because of concerns about community transmission of Covid-19.
Dame Helen Winkelmann said the wearing of masks is also encouraged at courts elsewhere in the country.
In Auckland, people will be offered a mask if they do not have one of their own.
Meanwhile, the government is encouraging people in South and West Auckland to get a Covid-19 test whether or not they are showing symptoms.
It says people who live in those areas, or who are at greater risk of poor health outcomes, should get themselves tested.
The prime minister will confirm today at 1pm whether Auckland will go to alert level 2 from Monday.