A spokesman for the Refugee Action Coalition, Ian Rintoul, says the protests outside Villawood detention centre and Holsworthy barracks were successful.
The protesters were calling for the release of all detainees.
Mr Rintoul says that the protests highlighted that the plight of refugees is still of paramount importance to many Australians.
He says many of the protesters came from a diverse range of backgrounds, and were concerned about the government's announcement that refugees who arrive by boat could be processed offshore.
"We weren't actually able to get in and see the detainees at Holsworthy but we certainly made the point at the gate of Holsworthy. I think we had a really good presence. I think we had about 200 people at Holsworthy. We are now outside the Villawood Detention centre, at the side entrance to the centre."
The protesters will be camping out near Villawood over the long weekend.