Was a huge fan of Marlon Brando, since seeing his screen debut in the movie The Men (1950). As a teenager, Seberg wrote to Brando and invited him to stay with her parents in Iowa. She met him years later and Brando asked her to renew the invitation.
Was in serious consideration for the role of Lara in Doctor Zhivago (1965), which went to Julie Christie.
Wrote and published an open letter to drug addicts' in the daily paper Libération: 27th February 1978.