The European football governing body said that they had taken the decision to ban the Argentine "for discriminatory (i.e. homophobic) conduct", with three of those matches suspended for a two-year probationary period.
UEFA said that Prestianni, 20, had already served one of those matches in the second leg of the Champions League play-off against Madrid.
The winger was provisionally banned for that game after Madrid star Vinicius Junior accused him of racism when they clashed in the first leg on February 17th, which Prestianni denied.
As the two argued, Prestianni spoke to Vinicius while covering his mouth, with the Brazilian subsequently complaining to the referee, leading to the match being suspended for 10 minutes.
Real's Aurelien Tchouameni said after the game that Prestianni had told him that he had not racially abused Vinicius but instead called him a homophobic slur.
UEFA said that they were asking world football governing body FIFA "to extend worldwide the above-mentioned suspension".