Emergency crews battled a blaze on Sheppard Street in the Maples Sunday night.
It happened around 9:00pm near Margate Road.
The three people in the home were able to escape as heavy smoke billowed out of the basement of the duplex.
As fire fighters attacked the flames the people in the adjoining part of the building were also evacuated as a precaution.
There is no estimate of damage but fire officials say the incident is under investigation.