Jefford made many appearances for the Royal Shakespeare Company, the National Theatre and the Old Vic, playing almost every available classical role.
She also appeared on screen, earning a nomination for best British actress at the Bafta film awards in 1968 for playing Molly Bloom in Ulysses.
Her agents said she was "warm and generous" and "a sensational actress".
A statement from United Agents said: "In the course of an extraordinary 70-year career, Barbara has graced the screen within TV and film, but it was on stage that she truly felt at home."
