The Brazilian, 33, was found guilty of assaulting a 22-year-old woman along with five other men at a disco in Milan in 2013, when he played for AC Milan.
Robinho has the right of appeal and the sentence will not be enforced until that process has been completed, according to Sky Sports.
He played more than 40 games for Manchester City between 2008 and 2010 after signing from Real Madrid for £32.5m, at the time making him the most expensive player in British football.
He then went on loan to Brazilian side Santos, before joining Milan.
Robinho is currently in Brazil where he plays for Atletico Mineiro.