In July 2019, Avdija led Israel to a second straight gold medal at the FIBA U20 European Championship in Tel Aviv. He averaged 18.4 points, 8.3 rebounds, 5.3 assists, 2.4 blocks, and 2.1 steals per game, earning MVP and all-tournament team accolades, as the second-youngest player at the event. Avdija tallied 26 points, 11 rebounds and 5 steals against France in the semifinal, before recording 23 points, 7 assists, 5 rebounds, and 3 blocks against Spain in the final.