The fire was already out when the firefighters arrived, said Northern Fire and Emergency NZ shift manager Josh Pennefather.
"One person has sustained burns," he said. "A fire investigator will be returning this morning."
St John sent a helicopter and two ambulances to the Old Taupo Rd facility.
One patient was treated and taken to Rotorua Hospital in a critical condition, a spokesperson said.
Cantabria Lifecare & Village has 236 beds and provides geriatric, medical, physical, intellectual and dementia care, according to the Ministry of Health.