Bišćan named his 23-man squad for the group stage of the tournament on 9 March 2021. However, during the month, several important players were ruled out due to injuries, such as Boško Šutalo, Joško Gvardiol, Luka Sučić and Borna Sosa. After the opening match, the 1–0 loss to Portugal on 25 March, Bišćan was criticized for his "catenaccio" tactics that were deemed uncharacteristic for Croatian football, which is best known for its midfielders. Three days later, Bišćan led Croatia to their first ever victory at the European Under-21 Championships, beating Switzerland 3–2. However, despite losing 2–1 to England in the final group game on 31 March, Croatia qualified for the quarter-finals for the first time in their history due to a better goal difference.