Balotelli, who joined rivals AC Milan from Manchester City last month, was the target of abuse by Inter fans during their 3-1 home win over Chievo Verona.
Serie A said in a statement that Inter had been fined because their fans "directed insulting chants and expressions of racial discrimination towards the player of another team."
Balotelli, who joined Inter in 2007 before moving to City in 2010, had upset Inter fans during his time at the club by wearing an AC Milan shirt on a television programme.
Milan and Inter are due to meet in Serie A on Feb. 24 and Inter president Massimo Moratti said he hoped there would be no repeat of the abuse.
"I am very sorry," he told reporters when asked about Sunday's events. "I hope it doesn't happen in the derby."