Dee was born Ruby Ann Wallace in Cleveland, Ohio, though she grew up in Harlem, New York. A 1945 graduate of Hunter College with degrees in French and Spanish, Dee made several appearances on Broadway before getting national recognition for her role in the 1950 film, The Jackie Robinson Story. Her acting career has crossed all major forms of media over a span of 8 decades, including films such as A Raisin in the Sun (in which she recreated her stage role as a suffering housewife in the projects) and Edge of the City both opposite Sidney Poitier. During the 1960s, Dee appeared in such politically charged films such as Gone Are the Days and The Incident, which paved the way for young African American filmmakers and actors. She has been nominated for seven Emmy Awards, winning once for her role in 1990's Decoration Day.

Ruby Dee and her late husband, actor Ossie Davis, were well-known civil rights activists. Dee is a member of such organizations as CORE, the NAACP, the Student Nonviolent Coordinating Committee and Southern Christian Leadership Conference. Their son is blues musician Guy Davis. Dee and Davis were personal friends of both Martin Luther King, Jr. and Malcolm X, with Davis giving Malcom X's eulogy at his 1965 funeral.