When she was eight, Moore's family left New York City and moved to Los Angeles at the recommendation of Moore's uncle, an MCA employee. She was raised Catholic, and had attended St. Rose of Lima Parochial School in Brooklyn until the third grade. She then attended Saint Ambrose School in Los Angeles, followed by Immaculate Heart High School in the Los Feliz neighborhood of the city. Moore's sister, Elizabeth, died at 21 "from a combination of... painkillers and alcohol", while her brother died at the age of 47 from kidney cancer.