Police in riot gear, supported by an armoured SWAT vehicle and a helicopter overhead, repeatedly ordered the crowd to disperse.
They then let loose with a volley of tear gas just after 23:00, sending the crowd, smaller than the one that clashed with police on Sunday scurrying.
The standoff occurred near the residential street where 18-year-old Michael Brown was fatally shot by a local police officer in this St Louis suburb.
Pathologists retained by Brown's family said early on Monday that the student had been shot at least six times, including twice in the head.
His death triggered daily protests and nightly clashes with law enforcement officials, and prompted the deployment earlier on Monday of National Guard reservists.