Firefighters say a fire was set in two different floors at the St-Michel offices of CPAM 1610 just before 4 a.m.
When emergency crews arrived at the scene, they found the front window of the Crémazie Boulevard building broken.
Emergency officials said the fires did cause damage, but didn't give a cost estimate.
No one was hurt.
The fires were deemed suspicious, and the Montreal police arson squad is now investigating.
CPAM is a popular French-language AM station that caters to the city's Haitian, Hispanic and African communities.