State media said that Ms Alidoosti, 38, was detained on the charge of “spreading falsehoods” about the protest movement.
It comes just days after she condemned the execution of a man over his involvement in the protests in an Instagram post.
In the post, she posed without a headscarf alongside the caption “Woman, life, freedom” in Kurdish – a popular slogan in the demonstrations.
She criticised international organisations for not speaking out against the execution of Mohsen Shekari, who was hanged after state authorities accused him of being a “rioter”.
He was also accused of wounding a protester with a knife and blocking a road with his motorbike alongside one of his friends.
Ms Alidoosti’s post read: “His name was Mohsen Shekari. Every international organisation who is watching this bloodshed and not taking action, is a disgrace to humanity.”
State news agency IRNA reported that Ms Alidoosti was arrested by police for failing to provide “documents in line with her claims”.
Ms Alidoosti is best known for her role in “The Salesman”, which won an Academy Award in 2017.
The protests were sparked by the September 16 death of Kurdish woman Mahsa Amini, who was arrested by the country’s morality police for not wearing “appropriate attire”. The demonstrations have snowballed into one of the most significant challenges facing the ruling regime since the 1979 revolution.
Iranian officials have blamed Ms Amini's death on pre-existing medical problems and claim the unrest has been caused by foreign enemies, including the United States.
Since the start of protests, at least five female Iranian actresses have posted pictures of themselves without the compulsory hijab in solidarity with the demonstrations in which women have played a leading role.