Born Clare Woodgate in Colchester, Essex, she attended Colchester County High School for Girls and broke into television acting when she was only sixteen years old, playing the role of Jenny on the BBC's 2point4 Children. After two series she left the show to concentrate on acting in television drama such as Casualty and in low budget films.

In 1995, Cates (then still known as Clare Woodgate) applied for the role of Stella in the film An Awfully Big Adventure but couldn't gain an audition. She returned home, dyed her hair red, and re-invented herself as a 16-year-old Liverpudlian girl called Georgina Cates who had no previous acting experience. When she re-applied for the same role, the casting director hired her.

Cates went on to co-star in such films as Frankie Starlight (1995), Illuminata (1998), and A Soldier's Sweetheart (1998). She received critical acclaim for her role as Amanda in the Clay Pigeons (1998) with Vince Vaughn and Joaquin Phoenix. After a seven-year break from the movie industry, Cates returned to the independent film genre to co-star in Sinner, for which she won a Best Actress award at the Brooklyn Arts Council International Film & Video Festival.

In 1997, Cates married American actor Skeet Ulrich with whom she had twins. The couple separated in 2004, and divorced in 2005, citing irreconcilable differences.