Sylvia Sidney was born Sophia Kosow on August 8, 1910, in The Bronx, New York City, to Jewish parents of Russian and Romanian descent. Her parents, who divorced shortly after her birth, remarried, and her mother's new husband, Sigmund Sidney, adopted Sophia.
As a shy and only child, Sylvia's parents encouraged her to be more outgoing and gregarious. She decided to pursue a stage career at the age of 15 and enrolled in the Theater Guild's School for Acting. Her early performances received rave reviews, and she began to appear in stage productions in New York and Washington, D.C.
Sylvia made her film debut in 1927 with the movie "Broadway Nights" and went on to appear in several more films throughout the 1920s and 1930s. Her breakthrough role came in 1931 with "City Streets," which made her a star. She continued to appear in a string of successful films throughout the 1930s, including "Ladies of the Big House," "Merrily We Go to Hell," and "Madame Butterfly."
In the 1940s, Sylvia's film career slowed, and she appeared in fewer movies. She took a four-year hiatus from acting and returned with the film "Blood on the Sun" in 1945. She continued to appear in films and television throughout the 1950s and 1960s, although at a slower pace.
Sylvia's most notable film roles in the 1970s and 1980s included "Summer Wishes, Winter Dreams" and "Beetlejuice." She appeared in a few more films in the 1990s, including "Mars Attacks!" and "Fantasy Island."