In 2009, Mamić was sued by
Eduardo da Silva for unfavorable contract according to which had to pay 20-25% of salary for the entirety of the career to Mamić's family, and Silva won the case in 2014.
On 18 November 2015, Mamić along with five other people was arrested over transfer irregularities in Dinamo Zagreb. He was suspected of tax evasion and bribery.
On 6 June 2018, Mamić was sentenced on first instance to six and a half years prison for transfer fraud relating to
Luka Modrić and
Dejan Lovren's transfer to
Tottenham Hotspur and
Olympique Lyonnais respectively. Mamić, his brother
Zoran, former Dinamo director Damir Vrbanović and tax official Milan Pernar, were all found guilty of siphoning over €15m from Dinamo and defrauding the state budget over €1.2m in unpaid taxes. Mamić, who had crossed the border into
Bosnia and Herzegovina one day earlier, did not attend the sentencing and stated that he would not be returning to Croatia. The
Court of Bosnia and Herzegovina refused to extradite Mamić since he also has the citizenship of Bosnia and Herzegovina