Lita Grey was 16 when she married the 35-year-old Charles Chaplin in 1924. Sydney was born two years later in Beverly Hills. His parents divorced a year later. Their elder son, Charles Chaplin, Jr. died in 1968.
After serving in World War II, including a stint in Europe, Sydney turned to acting.
Sydney was a founding member of the Circle Players at The Circle Theatre, now known as El Centro Theatre.
He won the 1957 Tony Award for Best Performance by a Featured Actor in a Musical for Bells Are Ringing, opposite Judy Holliday, and received a Tony nomination for his performance as Nicky Arnstein, the gambling first husband of Fanny Brice, opposite Barbra Streisand, in the Broadway musical Funny Girl in 1964.
Sydney appeared in two of his father's films, Limelight (1952) and A Countess from Hong Kong (1967).
He was also half-brother to Geraldine Chaplin, Michael Chaplin, Josephine Chaplin, Victoria Chaplin, Eugene Chaplin, Jane Chaplin, Annette Chaplin, Christopher Chaplin and Norman Chaplin.