Prisoners at Spring Hill Corrections Facility were evacuated on Tuesday night after one of them started a fire in his cell.
Staff at the prison, located halfway between Hamilton and Auckland, "quickly extinguished the fire", a spokesperson said.
Fire and Emergency was called as a precaution, and some prisoners were evacuated to a recreation yard due to the smoke.
They were returned to their cells once the danger was over. Corrections said there "was no threat to the wider security of the prison".
Two staff were taken for a medical check-up offsite, Corrections said.
NZ Herald reported police did not get involved.