The trial was held amid Greece's worst protests in decades, triggered by the killing of a 15-year-old Alexis Grigoropoulos by police in Athens.
Dozens of young people picketed the court, shouting anti-police slogans and hurling eggs and stones at the building.
26-year-old Augoustinos Dimitriou was seriously injured after being beaten by a group of police officers on November 17, 2006. The attack was secretly filmed and caused outrage in Greece.
The court sentenced eight police from 15 to 39 months in prison. Three other police officers and their chief were given 15-month suspended sentences for an attempt to conceal the beating.
The injured student said he was satisfied with the court ruling, but that he still suffered from stress as a result of the attack.