Mischa Barton was born in Hammersmith, London, United Kingdom to an Irish mother, Nuala (née Quinn), a photographer, and an English father, Paul Marsden Barton, a foreign exchange broker. She has two sisters, Hania and Zoe. Barton moved to New York City at the age of five and became a naturalised citizen of the United States in Los Angeles on 3 February 2006. Barton graduated from the Professional Children's School in Manhattan in 2004, and attended classes at The Royal Academy of Dramatic Art in the summer 2006.