Costello was also a lifetime member of The Actors Studio and an original player with the Lincoln Center Repertory.

Waltons actress Mariclare Costello dies at 90

Costello was also a lifetime member of The Actors Studio and an original player with the Lincoln Center Repertory.

By Mekishana Pierre

Mekishana Pierre

Mekishana Pierre is a news writer at **. She has been working at EW since 2025. Her work has previously appeared on Entertainment Tonight and Popsugar.

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April 27, 2026 3:20 p.m. ET

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Mariclare Costello in 1970 film 'Pound'. Credit:

United Artists/Getty

- Mariclare Costello, actress and lifetime member of The Actors Studio, died April 17 at 90 years old.

- Costello made her film debut in 1967, then appeared on several TV series including the first five seasons of *The Waltons* as Rosemary.

- "She made every space she inhabited more beautiful," her family said in their announcement. "[She] was always up for an adventure, especially if she could show up a few minutes late, as was her general inclination."

Mariclare Costello, a lifetime member of The Actors Studio who had a recurring role as Rosemary Hunter on *The Waltons*, died April 17 in Brooklyn, her family announced. She was 90.

In a heartfelt tribute to their loved one, Costello's family wrote that the actress' gift "was rare; she knew how to get people out of their own heads, focused on a task rather than on themselves, and in doing so helped them access their own creative voices."

They continued: "She was also, in every dimension of her life, someone who paid attention. She could talk to anyone, was interested in everything, and was a relentless asker of questions," the tribute continues. "She made every space she inhabited more beautiful. Warm, curious, generous and tough, she had the constitution of an ox, was never sick, and was always up for an adventure, especially if she could show up a few minutes late, as was her general inclination."

Mariclare Costello in 1971 cult horror movie 'Let's Scare Jessica to Death'.

Paramount Pictures/Getty

Born February 3, 1936, in Peoria, Illinois, Costello was raised the youngest of three daughters. Her mother, Margaret, was secretary to the Speaker of the Illinois House of Representatives in Peoria and Springfield, and her father, Dallas, was a civil engineer for the Illinois Department of Transportation. She graduated from Clarke College in Dubuque, Iowa, before receiving her master's in Theater and Education from Catholic University in Washington.

In 1964, Costello became an original member of the Lincoln Center Repertory Company — chosen as one of just 30 to be selected — led by Herbert Blau and Jules Irving.

She worked at Sheridan Square Theater, The Public Theater, and on Broadway, and was a lifetime member of The Actor's Studio, training alongside the likes of Jerome Robbins, James Earl Jones, José Quintero, Hal Holbrook, Austin Pendleton, and Faye Dunaway.

Costello made her Broadway debut in 1965 in a revival of *The Country Wife *alongside Stacy Keach. She later appeared three more times, in 1968's *Lovers and Other Strangers*, 1969's *A Patriot for Me,* and then 1970's *Harvey*, in which she played the psychiatric hospital nurse Ruth.

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It was in an acting class that she met her future husband, Allan Arbus, whom she moved to Los Angeles with in the 1960s. Arbus went on to play psychiatrist Major Sidney Freedman on CBS' *M*A*S*H, *and the pair were married from 1977 until his death in 2013 at age 95.

Costello made her film debut in 1967's *The Tiger Makes Out* starring Eli Wallach and Anne Jackson, then appeared on several TV series, including as Rosemary on 15 episodes of *The Waltons* during its first five seasons. She also appeared on the 1969 cop show *N.Y.P.D., *the 1971 horror film* Let’s Scare Jessica to Death, *1974 TV movie *The Execution of Private Slovik,* and 1980's *Ordinary People.*

Other TV credits included episodic roles throughout the 1970s, ’80s and ’90s in, among others, *Ironside, Kojak, Little House on the Prairie, Lou Grant, Murder She Wrote, Santa Barbara, Chicago Hope, Judging Amy,* and, in the early 2000s, TV movie *Shadow of the Blair Witch* and series *Providence*.

Allan Arbus and Costello in 2007.

Ryan Miller/Getty

Later in life, the actress led the drama program at St. Paul the Apostle Elementary School in Westwood and directed plays at Loyola High School and Loyola Marymount University, where she also taught acting for many years. She also directed productions for Interact Theater and led a theater group at Homeboy Industries, the gang rehabilitation and re-entry program.

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Costello is survived by her daughter, the stage director Arin Arbus, and Arin's partner, the playwright Ethan Lipton; granddaughter Bird; stepdaughters Amy and Doon; six nieces and a nephew.

A funeral service will be held in New York City, with burial and remembrance in Peoria.

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