Auckland Mayor Phil Goff says the ban on plastic bags is great news for the city and environment.
A national ban on most single-use plastic bags came into force on Monday, in a bid to improve our oceans and to protect animals.
Goff said the transition to reusable bags in supermarkets had been smooth.
"It's 800 million plastic bags going into our waste streams each year - that's less plastic bags clogging up our waterways," he told Newshub.
"I first took it up with supermarkets just under three years ago, and I said, 'Look, we really don't want these plastic bags going into the waste stream.'"
Goff said within two years supermarkets had reversed their positions and were in favour of a ban.
Prime Minister Jacinda Ardern said most people would seek to follow the rules.
Meanwhile Greenpeace is calling on the Government to step up and introduce a plastic-free New Zealand plan. Spokesperson Jessica Desmond said it would need to be well thought-out.
"Plastic pollution is a huge threat - it seems like every other week we're seeing a marine mammal washed up with a stomach full of plastic," she told Newshub.
Mainstream supermarkets did away with plastic bags last year, but everything from local markets to your favourite takeaway shop will now have to abide.
Choose not to, and it could cost up to $100,000 if your business is reported.
"The focus is very much on education," Conservation Minister Eugenie Sage said.