The 39-year-old was killed in a targeted drive-by shooting outside Aeolos boxing gym in Vari, East Attica, on Monday morning.
The boxing gloves Berdesis wore while fighting, were placed on his white coffin.
Investigators believe the mafia-style execution of the 39-year-old, appears to be related to feuds between rival gangs.
The retired boxer was shot at least 10 times while sitting in the front passenger seat of a car. The bullets hit his body and head.
He worked as a doorman at popular nightclubs and provided security for businesses. He also had a criminal record and had served time in prison, while in 2015 he was charged by police over his alleged participation in an extortion racket but was later acquitted.
Authorities are intensifying their hunt for gangsters engaged in increasingly violent wars for turf and power.