Relatives of Nazanin Bahrami say the Iranian actress has been arrested by undercover police in central Tehran.
Bahrami was one of some 800 women to recently sign a statement denouncing the “systematic” sexual harassment and violence against women in the Iranian film industry and had called for a mechanism to ensure those responsible were dealt with.
Her relatives said Bahrami was returning home in the capital from work when she was surrounded by plainclothes police and taken into custody.
Her whereabouts are not known and officials have not commented on the situation.
In recent months, pressure has been building on Iranian authorities over women's rights.
In response, Iran's notorious Guidance Patrols, or morality police, have become increasingly active and violent, with videos emerging on social media appearing to show officers detaining women, forcing them into vans, and whisking them away for various infractions such as failing to wear a hijab while in public.