Mitchell was born on March 12, 1930, in Newburgh, New York. He started his career on The Smothers Brothers Comedy Hour in 1967. Mitchell was in What’s It All About, World? as himself in 1969.

In September 1970, ABC cast Mitchell in Barefoot in the Park based on Neil Simon’s Broadway play of the same name. The series cast members were predominantly black, making it the first American television sitcom since Amos ‘n’ Andy to have a predominantly black cast (Vito Scotti was the sole major white character). Barefoot in the Park had been a successful 1967 film starring Robert Redford and Jane Fonda. It was thought by ABC that placing Barefoot in the Park behind Bewitched would do well, but because that show was already in a slump, Barefoot in the Park never developed high numbers for the network. During its first few episodes, Barefoot in the Park developed behind-the-scenes strife that sealed its fate: Mitchell was fired due to “differences of opinion” with the series’ producers. Rather than replace Mitchell with another actor—and already disenchanted with the low ratings—ABC decided to cancel Barefoot in the Park in December 1970. In 1986, Mitchell was in Jo Jo Dancer, Your Life Is Calling, a semi-autobiographical film about Richard Pryor. In 2017, after a hiatus of thirty years, Mitchell returned to acting in A Kindred Soul.

He was a guest star in many television series such as The Mothers-in-Law, Here Come the Brides, That Girl, The Odd Couple, The Six Million Dollar Man, and Baretta. Mitchell starred in several made-for-TV movies, such as Voyage of the Yes, Cops, and Cindy. He also turned to directing television with such as Me & Mrs. C. in 1984 and episodes of 13 East in 1989–90. Mitchell wrote for television and made-for-TV movies such as The Scoey Mitchell Show in 1972, Just a Little More Love in 1983, and Handsome Harry’s. In addition, he ventured into production of television and made-for-TV movies such as Grambling’s White Tiger in 1981, Gus Brown and Midnight Brewster in 1985, and Miracle at Beekman’s Place in 1988. Mitchell also was on a number of television shows as himself such as Match Game from 1974 to 1979, Super Password in 1988, The Joey Bishop Show 1968–69, Hollywood Squares in 1968, and Tattletales from 1974 to 1978 and from 1982 to 1984.