The incident took place around 2:15 a.m. ET, according to Const. Jean-Pierre Brabant of the Montreal police.
The car was travelling west on Notre-Dame Street East when the driver lost control and crashed into a tree on private residential property.
The car then ricocheted off the tree and hit the home's balcony in a secondary impact.
Five young adults — four men and one woman — were in the car. Two passengers were pronounced dead in hospital; the other three are in critical condition.
The car was totalled and first-responders had to use the jaws of life to extract the passengers.
Brabant said speed played a factor in the collision. Police are still investigating whether alcohol played a role.
Notre-Dame Street East has since reopened between Marien and Laurendeau avenues.