She then voiced a character on the Nickelodeon cartoon series Ka Blam! Her first major film role was as the protagonist of Lawn Dogs (1997), an acclaimed drama co-starring Sam Rockwell.
She continued acting, appearing in major box office pictures such as the romantic comedy, Notting Hill (1999) and M.
C., about affluent teenagers with stormy personal lives who reside in scenic Orange County, California.
The role catapulted Barton into mainstream fame, and Entertainment Weekly named her the "It Girl" of 2003.
Barton has since appeared in the comedy remake St Trinian's (2007), the Richard Attenborough-directed drama Closing the Ring (2007) and Assassination of a High School President (2008).
She also appeared alongside Martin Sheen in Bhopal: A Prayer for Rain (2014) and garnered critical praise for her lead role in Deserted (2016).
Barton graduated from the Professional Children's School in Manhattan in 2004, and took a summer short course called Acting Shakespeare at The Royal Academy of Dramatic Art in London, in June and July 2006, after he directed her in Closing the Ring.