Ana Paula Alminhana Maciel on Wednesday was the first to leave detention, walking out of a St. Petersburg pre-trial jail holding a sign reading "Save The Arctic."
She did not make comments to journalists before getting into a car with her lawyer and heading for a hotel.
Russian courts have granted bail this week to 17 of the detainees — including one of two Canadians — who face charges of hooliganism, and hearings are scheduled for another 12.
Paul Ruzycki of Port Colborne, Ont., was granted bail Tuesday, while Alexandre Paul of Montreal is scheduled for his hearing on Thursday.
The 30 people aboard a Greenpeace ship were detained in September and have been in custody ever since.
It is unclear whether the foreign activists would be allowed to leave the country.
— With files from the Canadian Press