Barton later appeared in the independent drama, Lost and Delirious (2001) and guest-starred as Evan Rachel Wood's girlfriend on ABC's Once and Again (2001–02).
In 1996 Barton had a supporting role in Catherine Butterfield's Where the Truth Lies which opened at New York's Irish Repertory Theatre.
The New York Times also remarked that "the winning child actresses Brittany Boyd and Mischa Barton are already smart enough not to overplay the naivete and precocity of their respective characters." The New York production went on to win the OBIE Award for Best Play.
She was also celebrated by Glamour as the "Next Big Thing" In 2007, Barton appeared in the films The Oh in Ohio and the comedy film Virgin Territory with Hayden Christensen.
She also joined Shirley Mac Laine and Christopher Plummer in Richard Attenborough's war drama Closing the Ring.
Other television appearances include an episode of the Fox series Fastlane (2003).