Horne's first major professional engagement was in 1954, when she dubbed the singing voice of Dorothy Dandridge in the film "Carmen Jones". Until that point, she had worked as a background singer for several TV sitcoms, as well as recorded covers of popular songs of the early 1950s, which were sold in dimestores around the country for $1.98. She made an appearance on "The Odd Couple" as a character named "Jackie", her own nickname, a meek and nervous would-be singer who develops a crush on character Oscar Madison (Jack Klugman) and into a full-blown diva as well, playing the role of Carmen in Felix Unger's (Tony Randall) opera group production. She also sang on "The Tonight Show Starring Johnny Carson". She made her Los Angeles debut the same year when she performed the role of Hata in "The Bartered Bride" with the Los Angeles Guild Opera.