Police spokeswoman Anie Lemieux says officers were called to a home near the intersection of Goncourt and des Vendéens avenues on Sunday night.
She said the mother of the baby boy called the police around 7:30 p.m., saying she was worried because the child's father had left the house with him that afternoon but failed to return.
When police searched the home, they found the body of the father and the baby on the property.
Lemieux said investigators believe the incident is a murder-suicide. The parents were in the process of separating.
The mother was taken to the hospital to be treated for shock.