Irvine, 48, from Northern Ireland, is not thought likely to have to serve any time in prison because sentences do not usually come into effect until the appeals process has been exhausted and they are usually suspended with such short terms, the Italian news agency Ansa reported.
Gabriele Moratti, 35, son of former Milan mayor Letizia Moratti, was also given six months over their altercation, which happened in December 2008.
The pair are said to have come to blows in the Hollywood disco over a text message allegedly sent by Irvine to a woman who had just ended a relationship with Moratti.
They subsequently reported each other to the authorities, which led to a trial for injury in a case which lasted nearly three years.
It was reported that the pair were found guilty of "mutual injury".
Irvine raced for Italian glamour team Ferrari in Formula One from 1996 to 1999.
The pair reportedly blamed each other for the dispute that took place in the VIP section of the club.
Both accused the other of using a glass during the incident.