Immigration authorities will now begin accepting visitors with visas and those on student visas again.
Prime Minister Jacinda Ardern called it an "enormous moment", adding it was part of a "cautious process".
Most visitors will still need to be fully vaccinated, but there are no quarantine requirements.
The country's maritime border has also reopened, with cruise ships and foreign recreational yachts now allowed to dock.
New Zealand first announced a phased reopening plan in February. It allowed vaccinated citizens to return from Australia that month, and those coming from elsewhere to return in March.
In May, it started welcoming tourists from more than 50 countries on a visa-waiver list.
"We, alongside the rest of the world, continue to manage a very live global pandemic, while keeping our people safe," said Ms Ardern in a speech at the China Business Summit in Auckland on Monday.
"But keeping people safe extends to incomes and wellbeing too."