In a press release on January 23, Amnesty said he had been held incommunicado at an undisclosed location since his arrest on November 4, 2012.
Behrouz Ghobadi is the younger brother of internationally acclaimed film director and outspoken government critic Bahman Ghobadi, who lives in exile.
He has been accused of "acting against national security."
But his family says he has never been involved in politics and his only connection to dissident activities is working on several of his brother's films.
Amnesty describes Behrouz Ghobadi's detention as "one of a series of attacks on freedom of expression by the Iranian authorities."
The campaign to demand his release engaged prominent Hollywood directors and actors.