The charges include illegal assembly, mischief and assault.
A total of 57 workers are now facing criminal charges in the Aug. 18 incident where protesters burst into city hall and forced politicians to flee as demonstrators threw documents and other objects from desks.
Of those, 44 were arraigned a week ago.
Six firefighters have already been dismissed for taking part in the protest over proposed provincial government changes to public-sector pension plans.
Under the changes, workers would contribute a higher percentage to their plans.
The Montreal firefighters union called Thursday for a boycott of the world police and firefighter games to be held in Montreal in 2017.
The event usually draws about 10,000 participants from around the world.