She was born Giovanna Scoglio in Liverpool, England, to an aristocratic Sicilian father, Pietro Scoglio, and an Irish mother, Eileen Sullivan. Raised from infancy in Sicily, she moved to the United States at age fourteen where she studied and worked in New York City. She studied acting and in 1954 was signed to a contract by Universal Studios in Hollywood.

Using the stage name "Gia Scala," she made her motion picture debut in 1955 but personal problems plagued her and in 1958 she attempted suicide. She received wide recognition for her performance of "Anna" in the 1961 film, The Guns of Navarone but her successful career began to deteriorate as a result of a growing alcohol dependency and she was eventually let go from her studio contract.

Having British citizenship because of her birth, she moved to work in film in England but there her troubles only escalated. Suffering from severe emotional problems, aggravated by alcohol, she made another unsuccessful suicide attempt before returning to Hollywood where she eventually did end her life with a drug overdose in 1972.

Gia Scala is interred in the Holy Cross Cemetery in Culver City, California.