The march along Michigan Avenue traveled north from Congress Parkway to just north of the river.
Demonstators say they are standing up in solidarity with the people of Syria and denouncing the government's use of deadly violence against political opposition.
The UN estimates more than 7,500 people have died in the year-long conflict so far.
Saturday, the Syrian government launched a renewed assault against protestors and rebel fighters.
Syrian president Bashar Assad told UN special envoy Kofi Annan that political solutions are impossible with what he calls "terrorist groups" threatening his regime.