[1][2][3] Kozina started his youth career in RK Matulji before establishing himself in Zamet the premier handball club of Rijeka.

In 2015 Kozina turned down Croatian powerhouse Zagreb and transferred to SG Flensburg-Handewitt where he spent one season.

[5] On 8 December Kozina announced that he signed with Frisch Auf Göppingen and that he would be moving in the summer of 2017.

[6] Kozina playerd for the Bundesliga Stars team on 2 February 2018 against Germany scoring 4 goals for a win of 43:39.

In December 2016 Kozina was invited to national team training for the upcoming 2017 World Championship as a replacement for Marino Marić who was injured.