At 37 years old, Mischa Barton has this physical status:
Barton began acting at the age of eight, co-starring in the Off-Broadway premiere of the 1994 play, Slavs!, written by Tony Kushner. Vincent Canby of The New York Times praised Barton's "so fine" and "chillingly authoritative" performance. New York magazine also praised her as "a darling little girl, [that] exhibits consummate charm". She appeared in several other Off-Broadway productions, taking a lead role in James Lapine's Twelve Dreams alongside Marisa Tomei at Lincoln Center. Canby again praised Barton, noting that she "has a sweet gravity as the doomed Emma". 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." In 1997, she appeared alongside Dianne Wiest at The Public Theater in Naomi Wallace's One Flea Spare. The New York production went on to win the Obie Award for Best Play.
She made her film debut in Lawn Dogs, which won awards at film festivals around the world. Barton won critical favour for her role, with Janet Maslin of The New York Times praising her "poised" performance and Empire celebrating her "hypnotic central performance". Barton then appeared in Notting Hill (1999) and The Sixth Sense (1999). Both films were critically and commercially successful, respectively earning $363,889,700 and $672,806,292. She also starred in Pups, a "Dog Day Afternoon for the MTV generation", alongside Burt Reynolds; along with her co-star Cameron Van Hoy, film critic Roger Ebert called their work in the film "two of the most natural and freed performances I have seen by actors of any age."
Barton first appeared on television in 1994, playing a young Corvina Lang in flashbacks in the soap opera All My Children. In 1996, she returned to the show, replacing Michelle Trachtenberg in the role of Lily Benton Montgomery. She guest-starred in eight episodes of the television series Once and Again as Jessie Sammler's (Evan Rachel Wood) girlfriend, Katie Singer. In 2001, she returned to film and starred in the independent Canadian drama, Lost and Delirious, based on the novel The Wives of Bath by Susan Swan. The film was met with mixed reviews, but the performances of Barton and her co-stars Piper Perabo and Jessica Paré were widely praised. She also starred in Julie Johnson (2001) alongside Lili Taylor and Courtney Love, playing the daughter of a woman in a lesbian relationship. Barton also had a supporting role in the independent teen drama Tart (2001) with Brad Renfro and Dominique Swain.
Other television appearances include an episode of the Fox series Fastlane (2003). She also appears as the love interest in James Blunt's music video "Goodbye My Lover" (2005) and in Enrique Iglesias' music video "Addicted" (2003).
In August 2003, Fox premiered the television series The O.C., about affluent teenagers with stormy personal lives who reside in scenic Orange County, California. The show became an overnight success due to its large fanbase, and resulted in Barton's fame being increased through her role as Marissa Cooper. Barton departed from the show in the third-season finale in May 2006. During her time on the show, Barton garnered several Teen Choice Awards. She was also celebrated by Glamour as the "Next Big Thing". The O.C. dropped in ratings dramatically during its third and fourth seasons, and ended in early 2007.
In July 2006, Barton appeared on the British comedy variety show The Friday Night Project as a guest host. In 2007, Barton appeared in the films The Oh in Ohio and the comedy film Virgin Territory with Hayden Christensen. She also joined Shirley MacLaine and Christopher Plummer in Richard Attenborough's war drama Closing the Ring. Attenborough praised her, saying "her ability to convey pain and sadness, hopefulness and fear, is riveting". The Independent also noted that "she lends her character a beguiling vulnerability." She also appeared in the British comedy St Trinians (2007), appearing as a former head girl of that school advising current senior pupils on fashion and style. Later in 2007, Barton was cast in the international film produced by the Russian band t.A.T.u., called You and I. The film premiered at the Cannes Film Festival in May 2008 and was released theatrically in Russia in 2011.
She appeared in Assassination of a High School President (2008), co-starring Bruce Willis, which premiered at the 2008 Sundance Film Festival. The Hollywood Reporter praised Barton's "captivating" performance. She also starred in the horror film Walled In, which was released straight-to-DVD in March 2009. It received mixed reviews, but her performance was praised, with IGN calling her performance "terrific". Her next horror project, Homecoming, received a limited release in July 2009. Barton did not attend the premiere of the psychological thriller due to a medical issue. She also starred in the 2009 film Don't Fade Away. In early 2009 she began filming alongside Martin Sheen in Bhopal: A Prayer for Rain a biopic of the Bhopal gas tragedy.
In a December 2007 interview, she indicated she would return to television for the right project; "It's not that I dislike doing television at all. It would be interesting having more creative control over where the storylines go or the characters. But for the right thing, of course." In 2009 she starred as one of the main characters on The Beautiful Life a new series on The CW. The series was subsequently cancelled on 25 September 2009 after broadcasting two episodes. In December 2009, the technology company HP became the show's sponsor, airing the show's five episodes on YouTube. She guest starred on Law & Order: Special Victims Unit, played an endangered prostitute in an episode that aired on 3 March 2010. She has since mainly filmed horror and thriller projects, taking roles in The Sibling, Cyberstalker, a Lifetime television film and Apartment 1303 3D, the English-language remake of the Japanese horror film, Apartment 1303. Barton also appeared alongside Ryan Eggold in Mark Edwin Robinson's supernatural romance thriller, Into the Dark.
In May 2012, Barton discussed her recent preference for the horror genre, following roles in Homecoming, Apartment 1303 and Sibling "I literally became obsessed with that genre. I can't tell you. Because I never watched it when I was younger; it used to be way too terrifying for me." However Barton added that, "I think I've gone through my little phase, for the moment." In June, Barton appeared in Noel Gallagher's music video for Everybody's on the Run. In July 2012, Barton made her stage return in an Irish production of Steel Magnolias, playing Shelby. It premiered at the Gaiety Theatre, Dublin on 12 September, and a nationwide tour followed thereafter. After the premiere, Barton received praise for her performance. The Evening Herald wrote "Barton sparkles from the moment she steps on stage...Barton's Shelby is instantly magnetic".
On 8 March 2016, Barton competed on the 22nd season of Dancing with the Stars. She paired with professional dancer Artem Chigvintsev. On 4 April 2016, Barton and Chigvintsev were eliminated from the competition and finished in eleventh place. Later in 2016 Barton received praise for her role in the independent drama Starcrossed. Writing in the Los Angeles Times, Katie Walsh described how "Barton is a standout as the alluring, broken young woman who hides as much as she reveals." Barton was later critically recognized for her performance in Deserted, a psychological survival story written and directed by Ashley Avis. Barton plays Jae, a young woman recently released from prison who goes on a soul-searching journey into the desert with her brother Robin, played by Jackson Davis. "Barton is well-cast, grounded and burdened," and "...delivers one of her best performances in years." In 2018, Barton was cast in The Cat and the Moon, the directorial debut of Alex Wolff.
At the 2018 MTV Video Music Awards, MTV announced a reboot of The Hills entitled The Hills: New Beginnings, slated to premiere in 2019. Barton was announced as part of the cast of the new series. She did not return for the second season. Barton had a cameo appearance in Spree, which starred Joe Keery of Stranger Things and premiered at the 2020 Sundance Film Festival. In October 2021, Barton was tapped to play an aspiring detective Miranda Green in the crime thriller film Invitation To A Murder, directed by Stephen Shimek.