Born in Sumter, South Carolina, Capers attended Howard University and studied voice at the Juilliard School in New York City.
She made her Broadway debut in Jamaica in 1957 as the understudy for Adelaide Hall in the role of Grandma Obeah and took over the role when Hall left the show. Capers went on to appear in Saratoga and Raisin, for which she won the Tony for Best Actress in a Musical.
Capers was a familiar face to television audiences. In addition to a recurring role on The Fresh Prince of Bel-Air, she appeared in many television programs, including Have Gun Will Travel, Marcus Welby, M.D., My Three Sons, Mannix, The Waltons, Mork & Mindy, Highway to Heaven, St. Elsewhere, Murder, She Wrote, Evening Shade, The Golden Girls, Married with Children, The Practice and ER.
Capers appeared in such films as What's Love Got to Do with It (film), The Great White Hope, Lady Sings the Blues, The Toy, Teachers, Norwood, The North Avenue Irregulars, Ferris Bueller's Day Off and Beethoven's 2nd.
Capers founded the Lafayette Players, a Los Angeles repertory theatre company for African-American performers. She was the recipient of the National Black Theatre Festival Living Legend Award, the Paul Robeson Pioneer Award, and the NAACP Image Award for theatre excellence.
Capers provided the narration for the adventure game Gabriel Knight: Sins of the Fathers.