Estimates put the number of demonstrators at up to 7,000, approximately half the number organizers said they were expecting.
Protesters demanded that the government resign and that early general elections be held.
Among those who addressed the crowd was Zviad Dzidziguri, a leader of the Democratic Front opposition group in parliament.
"We have brought this government to power," he said. "We must now change it."
The protest was called after police quelled what they say was a riot at a Tbilisi prison.
Officially, seven inmates were killed during the police operation and another 22 were wounded. Some 12 security officers also sustained injuries.
Opposition leaders and a number of rights campaigners are calling for an investigation into the unrest. They also demand that steps be taken to curb rights abuses.
(Imedi TV, Novosti-Gruziya, Civil Georgia, AP)