Alidoosti, who has played in Asgar Farhadi's Oscar-winning "The salesman", has posted a picture of herself without a veil on Instagram - where she has more than eight million followers.
In her hands she also holds a sign that reads "Woman, life freedom" - a recurring phrase among those who have shown their dissatisfaction with the regime in Tehran.
The protests, now in their fourth week, began after 22-year-old Mahsa Zhina Amini was arrested by the country's notorious morality police when she was deemed to have violated Iran's strict dress code for women.
A couple of days later she was pronounced dead.