Justin Phongsavanh made his international debut for the United States at the 2019 Parapan American Games, where he won a gold medal in javelin. He represented the United States at the 2020 Summer Paralympics, winning a bronze medal. In June 2021, during the U.S. Paralympic Team Trials for Track and Field, Justin set the javelin throw world record with a distance of 33.29 meters and is aiming for gold in Paris 2024.