Beširović came through Académico de Viseu's youth setup, which he left in February 2015 to join Radnik Bijeljina.[2] He made his professional debut against Široki Brijeg on 28 February at the age of 21.[3] On 15 March, he scored his first professional goal against Slavija.[4]
His family moved to Portugal two years before his birth, in 1992, during the Yugoslav Wars. Beširović's father Nail, was also a professional footballer,[12] who played in Portugal most of his career.