Her mother is Irish and her father is English and she has two younger sisters, Hania and Zoe. When Mischa was six, she and her family moved to New York.
Mischa graduated from the Professional Children's School in Manhattan and later took a course at The Royal Academy of Dramatic Art in London.
Mischa Barton began acting when she was eight in Tony Kushner's play "Slavs!" She credits Tony Kushner as "the reason I act for a living." Other roles on stage followed, including parts in "Twelve Dreams," "Where the Truth Lies" and "One Flea Spare." She appeared in films such as "Notting Hill" and "The Sixth Sense."
But it was her role on the Fox series "The O.C." that made her a star. With her fame, came modeling opportunities. Mischa Barton worked for Calvin Klein, Bebe, Neutrogena, Keeds and more.
Mischa Barton has since been in a variety of roles on shows such as "Law & Order: Special Victims Unit," "Apartment 1303" and "The Sibling," among others. Mischa Barton told Allure, "If you're considered a 'pretty girl,' then you have a really hard time having people open up to find you roles, because they want to peg you as something. So I've chosen quite dark characters." She added in a separate interview, "It kind of irritates me that I'm seen as this pretty face. People also say I'm too thin. The truth is, pretty people aren't accepted as other people. It comes with all these stigmas" (askmen.com).
Mischa Barton does more than act; in 2008 she created her own handbag collection as well as a line of headbands. And in 2009, she became the face of Herbal Essences.
In 2006, Mischa Barton became a naturalized citizen if the United States.
Mischa said the part of her body she likes least is her derriere. "It's just not toned at all" (people.com).
Unfortunately, Mischa Barton is also known for her blushes with the law. In 2007, she was arrested in West Hollywood for suspicion of driving under the influence; ("I don't know what to say about it, except that I'm not perfect and I just don't ever intend to do something this stupid again") and in 2009, she was sectioned for two weeks under a 5150 that allows a psychiatrist to involuntarily confine a person if its believed the person is a danger to themselves.
Mischa Barton has been a spokesperson for Climate Star, an organization that fights global warming.
Mischa Barton splits her time between Los Angeles and an apartment in London and New York.