Koljić started playing football at a local club, before joining youth academy of Slovenian team Maribor in 2011.
He made his professional debut playing for Triglav against Olimpija Ljubljana on 26 October 2013 at the age of 18.
[8] In August, Koljić was transferred to Romanian outfit Universitatea Craiova for an undisclosed fee.
[9] He made his official debut for the team against Dinamo București on 1 September and managed to score a goal.
[12] In January 2018, Koljić received his first senior call-up to Bosnia and Herzegovina, for friendly games against the United States and Mexico.