Mobley played for the United States at the 2018 FIBA Under-17 World Cup in Argentina. In seven games, he averaged 9.3 points, 5.6 rebounds and 2.6 assists per game, helping his team win the gold medal. Mobley joined the United States for the 2019 FIBA Under-19 World Cup in Heraklion, Greece, but he was limited to playing two games and a total of seven minutes in the tournament due to back spasms. His team won the gold medal despite his absence.