Alen Halilovic broke into professional football with Dinamo Zagreb at 16. His promise earned him a permanent switch to Barcelona, where he spent two years before moving on to Hamburg for another two seasons.
At the Nou Camp, he featured mainly for Barcelona B and spent the 2015–16 campaign on loan at Sporting Gijon.
After signing for Hamburg in 2016, he was loaned to La Liga side Las Palmas for the 2017–18 season.
In 2018, shortly after turning 22, he joined AC Milan—the sixth club of his career—making Italy the fourth country in which he had played.
He later had stints with Birmingham City and Reading, and he now represents Fortuna Sittard in the Netherlands.