NK Slaven Belupo
He made his Prva HNL debut on 7 November 2014, a day after his 21st birthday, in the 1-0 away loss to NK Slaven Belupo. Majstorović established himself, however, as the first team regular in the autumn part of the 2015/16 season, missing only a single game in the first 11 rounds, due to three yellow cards.