HŠK Zrinjski Mostar
On 20 February 2019, Mandić moved on a one-year loan to HŠK Zrinjski Mostar in the Premier League of Bosnia and Herzegovina. He made his debut for Zrinjski in a 0–1 home loss to FK Sarajevo in the 2018–19 Bosnian Cup. Mandić scored his first goal for Zrinjski in a 0–1 away win against FK Sarajevo in the 2018–19 Bosnian Premier League season.