Born in Melbourne, Victoria to a French-born artist mother and Australian entrepreneur father, Mitchell spent most of her childhood in Australia with her two older brothers. She studied ballet from age 4 to 16.
Mitchell finished in the top 1% of her graduating year, with an International Baccalaureate diploma. She attended Melbourne University, with the intention of becoming a lawyer. Mitchell completed her undergraduate degree in Arts: Media Communication, before moving to Los Angeles to pursue acting.
Penelope is the granddaughter of Lester Mitchell, MBE, and Heather Mitchell, OBE, prominent agriculturalists and political activists. Heather Mitchell was the first female president of the National Farmers Federation, and the co-founder of Landcare Australia, with former Victorian Premier Joan Kirner.
She is a cousin of actress Radha Mitchell.
