James Cellan Jones was born in 1931 in Swansea, Wales. Born into a family of doctors,he studied natural sciences at St John's College, Cambridge University, where he received his BA in 1952, later raised to an MA in 1978.Cellan Jones's true interest was acting and directing, however,[and he began working at BBC Television in 1955 as a callboy, and rose steadily to become a production manager. In 1960 he began directing for the BBC, and by 1965 was directing several major productions a year there. In 1967 he directed seven episodes of the award-winning miniseries adaptation of The Forsyte Saga, and his other period dramas have included numerous adaptations of works by Henry James and George Bernard Shaw. In the 1970s he directed two notable historical biographical sagas: the award-winning miniseries Jennie: Lady Randolph Churchill (1976), and the 13-episode miniseries The Adams Chronicles (1976), about the American Adams political family.
From 1976 through 1979 Cellan Jones was Head of Plays at the BBC, where he was responsible for up to 85 productions a year. Upon leaving the post, he became a freelance television director, and continued to work steadily for 20 years. Highlights of this period include the World War II miniseries Fortunes of War (1987) starring Kenneth Branagh and Emma Thompson, and the award-winning television film Harnessing Peacocks (1993).
Cellan Jones was Chairman of BAFTA from 1983–1985.He has also been Chairman and Honorary President of the Directors Guild of Great Britain.