Dinamo Zagreb president Zdravko Mamic, who is suspected of tax evasion and bribery, has been arrested along with five other people.
Croatian HTV said Mamic's son, who is also a Dinamo official, was also among those arrested on Wednesday.
Mamic and his brother, coach Zoran Mamic, have been under investigation in connection with alleged corruption and organised crime.
Croatian authorities have accused them of embezzling the equivalent of $17.3 million of the club's money since 2008 and not paying $1.8m in state taxes.
Croatian media said they were suspected of taking undeclared commission fees from the sale of Dinamo players to foreign clubs.
Zoran Mamic was not arrested along with the group on Wednesday. The brothers were initially detained in July but released on bail.