Thousands of protesters, angered by a monthlong Mohawk blockade of a major commuter bridge, hurled bottles and rocks at police, who responded with tear gas.
At least 75 people, including 16 police officers, were injured but none of the injuries were serious, police said. Eighteen people were briefly arrested after the four-hour melee late Sunday at Mercier Bridge, which connects Montreal with its suburbs.
About 10,000 people participated in the demonstration at its peak.
Earlier, an agreement was signed between the Indians and the federal and provincial governments to start negotiations to bring down the Mohawk barricades.
The Indians are blocking the bridge to protest plans to expand a golf course on what they claim is sacred tribal land.