Mariclare Costello, the veteran stage and screen actress known for The Waltons and the cult horror film Let’s Scare Jessica to Death, died April 17, 2026, in Brooklyn, New York, at age 90.
Born in 1936 in Peoria, Illinois, she studied theater in Iowa, Vienna, and at Catholic University, where she trained under Viola Spolin and even performed for President John F. Kennedy.
Costello built a respected New York theater career before moving into film and television, appearing in Ordinary People, Buckaroo Banzai, The Execution of Private Slovik, and series like Kojak, Murder, She Wrote, and Chicago Hope. She is best remembered for her role as Rosemary Hunter on The Waltons.
She was married to actor Allan Arbus from 1977 until his death in 2013. Later in life, she focused on teaching and directing theater in Los Angeles, working with schools and community programs.