The woman, 68, was found dead in an apartment building on Laurier Avenue in Rosemont.
According to Const. Simon Delorme of Montreal police, the suspect is the woman's son.
On Friday, a police spokesperson confirmed the woman suffered serious stab wounds to her upper body.
A man discovered the woman at 9:30 a.m. ET on Friday. She was declared dead at the scene.
This is the 12th homicide to take place in Montreal this year. On this day last year, 18 homicides had been investigated.