Mischa Barton was born in Hammersmith, West London, England, an Irish mother, Nuala (née Quinn), a photographer and an English father Mancunian, Paul Marsden Barton, a foreign exchange broker. She has two sisters, younger and older Hania Zoe, a lawyer in London. Work of her father took the family to New York where Barton was six, and ten days after her twentieth birthday, she became anaturalized citizen of the United States in 2006. Keep her Britishnationality, Barton in reference to her roots English, said: "I feel more at home in England a long time", she stresses that "I like people to discern that I am an English-Irish girl who grew up in New York."
Barton graduated from the kids school professionals in Manhattan in 2004, and took a short summer course called Acting Shakespeare at the Royal Academy of Dramatic Art in London in June and July 2006, at the instigation Sir Richard Attenborough, after she ordered the closure of the ring.