Petracca was born to Elvira and Tony Petracca on 4 January 1996 and is of Italian heritage. He was recognised as an adept footballer at a young age when he represented Victoria at under-12 level. He played his junior football with the Park Orchards Football Club, Warrandyte Football Club and Beverley Hills Football Club. Apart from football, he was talented at most sports he played including cricket, soccer and tennis, but especially basketball. His leadership was recognised at a young age when he was named co-captain of the Victorian Primary Schools (VPS) basketball side. He featured in the under-16 Victorian basketball side and was selected in the Australian under-17 squad alongside 2014 NBA number-five draft pick and Utah Jazz player, Dante Exum. Basketball was his best sport as a junior, however, he decided to pursue a football career instead at sixteen years of age to stay in Australia and be closer to friends and family.