Steinfeld was born in Tarzana, Los Angeles. Her mother is Cheri (née Domasin), an interior designer. Her father is Peter Steinfeld, a personal fitness trainer. Her father is Jewish and her mother is of African American, English, Filipino, Irish, Scottish and German descent. Her maternal grandfather, Ricardo Domasin is a Filipino, from Bohol, Philippines. Her older brother, Griffin, is a stock car driver. Steinfeld calls him her best friend on some of her Tweets. She was raised in Agoura Hills and in Thousand Oaks, California. She attended Ascension Lutheran School, Conejo Elementary, and Colina Middle School. She has been home-schooled since 2008, because of bullying.