Shortly after midnight, firefighters arrived at the Avis Budget near the intersection of Langelier and Lavoisier boulevards.
Montreal police Const. Daniel Lacoursière said the molotov cocktail, which was thrown against the business's window, landed on the sidewalk in front of the building without breaking the window pane.
Lacoursière said the attack left no damages.
The same business was the target of an attack on May 10.
The Montreal Police arson squad will be on the scene Tuesday to investigate and meet with the owner of the business.