Brooklyn, N.Y. — Mariclare Costello, best known for her role as Miss Rosemary Hunter on the beloved television series "The Waltons," has died at the age of 90. Costello’s family announced her passing on April 17, 2026, marking the end of a prolific career that spanned six decades and enriched both stage and screen.
Born on February 3, 1936, in Peoria, Illinois, Costello was the youngest of three sisters in a family that nurtured artistic talents. She initially pursued her education at Clarke College in Iowa and later earned a master’s degree in theater and education from Catholic University in Washington, D.C. There, she studied under the renowned Viola Spolin, who introduced her to improvisational techniques. Costello showcased her early acting prowess in a performance of “The Merchant of Venice” for President John F. Kennedy.
Following her graduation, Costello embarked on a journey to New York City, quickly establishing herself as a vital member of the Lincoln Center Repertory Company. In 1964, she made her Broadway debut alongside Jason Robards in Arthur Miller’s "After the Fall," which marked the beginning of a remarkable run that included nine Broadway productions through 1970.
Her diverse stage career included roles in notable productions such as "But For Whom Charlie," "Tartuffe," and a revival of "Harvey" featuring screen legends James Stewart and Helen Hayes. Despite her roots in theater, Costello also made her mark in film and television.
Costello’s film career began in 1967 with "The Tiger Makes Out," but she garnered a devoted following for her chilling performance in the 1971 cult classic "Let’s Scare Jessica to Death." As Emily, a seemingly carefree figure who turns out to be a vampire, her haunting emergence from a foggy lake became a standout moment in 70s horror cinema. She also appeared in the acclaimed 1974 telefilm "The Execution of Private Slovik" and Robert Redford’s Oscar-winning "Ordinary People" in 1980.
From 1972 to 1977, Costello captured hearts as the compassionate schoolteacher on "The Waltons," a show that resonated deeply with American families. Her character, Miss Hunter, played a crucial role in supporting young John-Boy Walton’s aspirations as a writer. Later, she starred in the short-lived series "The Fitzpatricks" and made numerous guest appearances on popular television shows throughout the 70s, 80s, and 90s.
In addition to her acting career, Costello led a rich personal life. She met her husband, Allan Arbus—a former "MAS*H" actor—during an acting class, and they married in 1977. Their partnership lasted until his death in 2013. Costello was remembered not only as a talented performer but also as a teacher, a mentor, and an enthusiastic animal lover. Those close to her noted her genuine curiosity and ability to connect with people from all walks of life.
Costello is survived by her daughter, Arin Arbus, who is a stage director, her granddaughter Bird, and two stepdaughters, Amy and Doon. A funeral service is planned for New York City, followed by burial and a memorial gathering in Peoria, where her legacy will be celebrated by family and friends.