Six Montreal police officers were slightly injured and about 20 downtown buildings were vandalized.
Montreal police spokesman Jean-Pierre Brabant said two men were arrested and charged in connection with the incident.
A 25-year-old man was charged with armed assault on a police officer and a 24-year-old man faces one count of obstructing police.
Both were released Saturday afternoon on a promise to appear in court.
Brabant said police are analyzing video from the scene to try to identify more of the people involved.
Anti-riot police were called in to handle the incident, which took place downtown outside the popular FrancoFolies festival.
Several businesses, parked vehicles and Montreal police headquarters had their windows smashed.
Montreal Mayor Denis Coderre condemned the incident on Saturday, calling it “deplorable.”
“Montreal is the capital of living together,” he said. “It’s a safe area. There’s no need to break anything.”
The festival’s president said he didn’t believe security needed to be increased for the final concerts set to take place Saturday night.
“We have a very good (security) team, we work very closely with Montreal police, and I’m sure we’ll have a great night,” Jacques-Andre Dupont said.