The Ministry of Foreign Affairs says New Zealanders within 80 kilometre of the stricken Fukushima nuclear plant should leave.
Its warning was previously set at 20 kilometres.
The wider zone is much further out from the plant than even the Japanese government is recommending for its own citizens.
The ministry says the warning is a precautionary measure given the current state of uncertainty about the plant's radiation levels.
Since Friday's earthquake and tsunami, the ministry has confirmed the safety of 2,000 of 6,000 New Zealanders in Japan.
The last unaccounted for New Zealander has been found alive and well.
Peter Setter, 53, walked four kilometres to an evacuation centre so he could make contact with his parents in the Hawke's Bay town of Waipawa.
His father, Brian Setter, says his son was staying in a damaged home in the Japanese port city of Kesennuma where he went to visit friends before the disaster.
Mr Setter says the home does not have any electricity or any means of connecting to the outside world.
No plans to evacuate
Foreign Affairs and Trade Minister Murray McCully says there are no immediate plans to evacuate, but the ministry is talking to Air New Zealand to arrange emergency flights if needed.
Mr McCully says any New Zealanders who find themselves stranded should contact the New Zealand embassy. In some cases people may need to make their own way to a rescue team so they can be picked up, he says.
The ministry says New Zealanders returning home from Japan are highly unlikely to be contaminated or exposed to significant radiation and will not require checks for radioactivity.
Earlier, it advised New Zealanders in Tokyo to consider leaving if they do not have a pressing need to be in the capital.
The ministry said the advice also applied to earthquake and tsunami-affected provinces of Chiba, Fukushima, Aomori, Iwate and Ibaraki. It said the advice had been issued because of a lack of infrastructure in those areas.
The Australian government has already advised its citizens to leave Tokyo and Britain has told its citizens to consider leaving the capital and northern areas. France has advised its nationals they should leave Japan.