The County Court in Karlovac, 50 kilometres southwest of Zagreb, found Milan Cacic guilty of beating Croatian civilians in the Slunj area and intimidating them by threatening to shoot them, including a 12-year-old boy.
The court also found that he had been involved in large-scale looting and destruction of Croat-owned property, including the burning of at least seven houses.
Cacic was arrested in the northern Adriatic town of Pula on 21 October last year and has been in the custody of the Karlovac court since. He has the right to appeal.