Pokusevski was born December 26, 2001in Belgrade, Serbia (formerly Yugoslavia). He grew up in Novi Sad, where he began playing basketball for local teams. He broke onto the scene as a youth player for Olympiacos Pireaus, a Greek club. Pokusevski has dual-citizenship in Servia and Greece. At age 17, Pokusevski was promoted to the Olympiacos senior team, becoming the youngest EuroLeague player in club history. From there, his stock rose and he caught the attention of more NBA scouts. In 2017, he participated in the Jordan Brand Classic camp. He also played in the Basketball Without Borders Europe camp in 2018 and the NBA All-Star Basketball Without Borders Global Camp in 2019. Pokusevski played for the Serbian national under-17 team and the under-18 team in back-to-back seasons.