They said the case was not connected to the four previous cases.
"Significantly, there is no evidence of community transmission from any of these earlier cases," said a ministry spokesperson.
The Herald understands the new case was admitted to Waitakere Hospital on Friday night.
This comes after the ministry confirmed last month that a person who had recently returned from overseas was isolating in the South Island following a positive test result.
A third case of monkeypox was confirmed earlier in August after a person returned from overseas.
That person was also isolating in the South Island.
Two previous cases had been reported in New Zealand in July. By the end of the month, health officials reported they had since recovered.
Ministry public health advice for those with monkeypox is to isolate at home until the scabs from lesions have fallen off.
Monkeypox virus is part of the same family of viruses as variola virus, which causes smallpox.
Monkeypox symptoms are similar to smallpox symptoms, but milder, and monkeypox is rarely fatal. Monkeypox is not related to chickenpox.
The ministry is continuing to provide advice to public health units, primary health organisations and sexual health clinics to assist with identifying potential cases.
"Health professionals are being reminded to remain vigilant for any possible cases of monkeypox," they said.
"We continue to advise anyone who will have close physical or sexual contact while overseas, or with people who've recently been overseas, to be mindful of monkeypox symptoms and the health advice."
According to the World Health Organisation, the number of monkeypox cases reported globally declined by 21 per cent last week, reversing a month-long trend of rising infections and signalling Europe's outbreak may be starting to decline, the ministry said.
