Reports in Italy claimed City were keen to acquire the Slovakia international, who has also been a reported target of Chelsea and Manchester United.
However, Mancini said today he is not interested in the 22-year-old.
"Hamsik is not part of Manchester City's plans," he said.
Hamsik scored 12 goals in 37 league appearances for Napoli last season. He joined Napoli in the summer of 2007 and is under contract until June 2012.