Sobieski was born in New York City. Her mother, Elizabeth Sobieski (née Salomon), is an American film producer and screenwriter who also works as Sobieski's manager, and her father, Jean Sobieski, is a French-born painter and former actor of Polish and Swiss descent. Her maternal grandfather, United States Navy Captain Robert Salomon, was Jewish. Her maternal grandmother was of Ashkenazi Jewish and one quarter Dutch descent. Sobieski grew up in a "pan-religious" family; she has said that she is "proud of [her] melting pot roots". Her younger brother is Robert "Roby" Sobieski.
