She is best known for her role as young idealistic schoolteacher Alice Johnson in the ABC comedy drama series Room 222 from 1969 to 1974, for which she won the Primetime Emmy Award for Outstanding Supporting Actress in a Comedy Series in 1970, and received a Golden Globe Award nomination in 1971.

[4] In 1966–1967, she started her television career as "The Resident Dream Girl" on Chuck Barris's The Dream Girl of 1967, replacing Beverly Adams from the first weekday broadcast opposite hosts Dick Stewart and Wink Martindale, and during that time, she appeared on another Chuck Barris show, The Dating Game.

[14] She played the title role in the critically acclaimed true story Muggable Mary, Street Cop (1982).

Valentine appeared in many other movies for television including The Daughters of Joshua Cabe (1972); Coffee, Tea or Me?

Valentine was a semi-regular on The Hollywood Squares from 1971 to 1977 on both NBC-TV and in syndication, often trading quips with Paul Lynde.