Niagara Regional police say they were called to the scene of the blaze around 1:35 a.m. Friday morning.
They say the first officer on scene tried to get into the house, but was driven back by smoke and flames.
He then found a nearby garden hose and used it to fight back the flames enough to get inside.
He found the mother and child inside and led them to safety through a back door.
The occupants of the house were not injured, and police say the officer has been treated for minor smoke inhalation. His name is not being released and the cause of the fire is under investigation