By 1937 , Moorehead had joined Orson Welles ' Mercury Players , as one of his principal performers along with Joseph Cotten . ( In an appearance on '' The Dick Cavett Show '' on 19 February 1973 , she revealed that , in 1922 , she had by chance met Welles ( fifteen years her junior ) when he was a mere seven years old at the Waldorf-Astoria Hotel in New York City . ) She performed in his '' The Mercury Theatre on the Air '' radio adaptations , and had a regular role opposite Welles in the serial '' The Shadow '' as Margo Lane . In 1939 , Welles moved the Mercury Theatre to Hollywood , where he started working for RKO Pictures . Several of his radio performers joined him , and Moorehead made her film debut as the mother of his own character , Charles Foster Kane , in '' Citizen Kane '' ( 1941 ) , considered by most film critics as one of the best films ever made . Moorehead was featured in Welles ' second film , '' The Magnificent Ambersons '' ( 1942 ) , and received the New York Film Critics Award and an Academy Award nomination for her performance . She also appeared in '' Journey Into Fear '' ( 1943 ) , a Mercury film production
Academy Award nomination
15th Academy Awards
Agnes Moorehead