Kate Noelle Holmes was born in Toledo, Ohio, the youngest of five children. Her father, Martin Joseph Holmes Sr., was an attorney specializing in divorce law, and her mother, Kathleen A. Holmes, was a homemaker and philanthropist. Her upbringing in a close-knit, Catholic family instilled in her a strong sense of values and a grounded perspective that would later prove valuable navigating the complexities of Hollywood.

Holmes began her professional acting career in 1997, first appearing in the film 'The Ice Storm'. Almost immediately, she won one of the leading roles in the teen thriller 'Disturbing Behavior'. These early roles served as a launchpad for her career, giving her exposure and experience that would pave the way for her breakthrough role.