Front rower Cherif Traore wrote on Instagram that he received the unwanted present, inside a rubbish bag, during a Christmas dinner for Benetton Treviso players.
"Apart from finding it an offensive gesture, what hurt me the most was to see that most of my team mates who were present were laughing. As if it was all normal," he said.
"I haven't slept all night," the 28-year-old added.
Traore was born in Guinea but has lived in Italy since the age of 7.
He plays as a prop for the northern Treviso club and for the Italian national Rugby Union team.
He said he normally does not react to "racist jokes", in order not to "make enemies" with people around him, but said he could not let the latest insult pass.
"I decided not to keep quiet this time to ensure that episodes like this do not happen again," he said, adding that such behaviour would be "seriously condemned outside of Italy".
In a statement, Benetton Rugby said they have "always condemned with the utmost firmness any expression of racism and/or form of discrimination".
The incident involving Traore "has nothing to do with sport", and the club will always stand for "respecting people, their culture, their ethnicity, their faith and their dignity," the club said.
There have been numerous incidents of Black athletes in Italy suffering racist abuse.
In football, Black players are routinely abused by fans during games. In October, Paola Egonu, a Black volleyball player, announced she was taking a break from the Italy national team following comments questioning her nationality.