Born in Oak Park, IL, to a poor family, her parents divorced early on and she was educated at the Goodman Theatre in Chicago and the Actors Studio in New York. She was named Miss Chicago in 1948 and was a semi-finalist at the 1948 Miss America Pageant. Ms. Nettleton made her Broadway debut in 1949 in the short-lived Dalton Trumbo comedy The Biggest Thief in Town. A role in Sidney Kingsley's Darkness at Noon in 1951 proved luckier, providing work for half a year.
After roles in God and Kate Murphy (for which she won a Clarence Derwent Award for best supporting performance), Silent Night, Lonely Night and The Wayward Shock, she didn't play Broadway for nearly a decade, returning as successor to Rosemary Harris in Ellis Raab's 1973 revival of Streetcar at the Repertory Theatre of Lincoln Center. She won admiring reviews. Surrounded by a different cast and guided by a new director, Jules Irving, she returned to the role that fall at the St. James Theatre.
Ms. Nettleton was nominated for a Tony Award and Drama Desk Award for her work in a 1976 Phoenix Theatre revival of Sidney Howard's They Knew What They Wanted. Her final Broadway role was in Stranger in 1979.
She was married to humorist Jean Shepherd from 1961 to 1967. The two met when Ms. Nettleton called Shepherd's nightly radio show at WOR in the 1950s. She became a frequent guest, known to listeners only as "The Caller." The two appeared together in Shepherd's 1959 Off-Broadway play Look Charlie.
Her film and television roles included "A Face in the Crowd," "Studio One," "The Twilight Zone," "Route 66," "The Fugitive," "Bonanza," "Gunsmoke," "The Man in the Glass Booth," "In the Heat of the Night," and three years on "General Hospital." In 2004, Ms. Nettleton starred Off-Broadway in Mark Giesser's short-lived comedy, How to Build a Better Tulip, playing a botanist. In 1991, she played Desiree opposite John McMartin in Center Theatre Group's staging of A Little Night Music in Los Angeles.