The Hamilton Fire Department (HFD) said they were called to a two-story residence on Garden Crescent at approximately 6:30 p.m.
Crews arrived and encountered heavy smoke. HFD said firefighters quickly entered and searched the home after reports that someone was inside.
A child was pulled from the home and taken to a local hospital, HFD said.
According to Hamilton doctors, a total of 13 people were taken to hospital, including 10 children between the ages of two and 17.
One of the children, a five-year-old, is in danger for his life. The others were taken to be evaluated for smoke inhalation and are now in stable condition.
Rescuers added that the other three victims were adults – one man and two women. They said the man was sent to a burn center for smoke inhalation.
The cause and origin of the fire are unknown.