The guesthouse comprises a mix of one and two-bedroom units, rented out at between $140 and $240 a week.
The manager of the guesthouse, Ofa Hoskin, said she believed a heater may have been responsible for the blaze.
She said it was isolated to one part of the building. She said the building was equipped with smoke alarms and was directly linked to the fire department.
The Wembley guesthouse in Otahuhu. Photo / Google Maps
She said the person who died was a male.
She said the building is owned by a Singaporean company.