Four family members were inside the home on Activa Avenue when the explosion happened just before midnight on Sunday.
When firefighters got to the scene, they found three of the four family members outside the home.
A teenage girl was still missing, but firefighters found her alive and conscious minutes later, beneath the rubble.
"She was discovered underneath some rubble at the rear of the property," said Tom Ruggle, the chief fire prevention officer in the Kitchener Fire Department.
All four family members were treated in hospital. Two siblings and their mother have been released, while their father remains there.
Many residents reported feeling their own homes shake when the blast occurred. One said "it sounded like an earthquake."
The cause of the explosion may not be known for days.