Of Italian descent, Mancuso was born in Reno, Nevada, and grew up in the nearby Lake Tahoe area as the middle of three sisters, between older sister April and younger sister Sara. Her father, Ciro Mancuso, was arrested at the family home when Julia was five years old, and was later convicted of running a $140 million marijuana smuggling operation. Her parents divorced in 1992, and her mother Andrea ("née" Tuffanelli) said that Julia "took everything out on the slopes." After his release from prison in 2000, Julia and her father became close. Ciro's sentence was greatly reduced because of his cooperation with the government in cases against other alleged organization members and Mancuso's lawyer Patrick Hallinan. As a result of his assistance to the government, Ciro Mancuso was allowed to keep $5 million in proceeds from his trafficking business.