"Is it possible to go to the World Cup without him? Absolutely not," Prandelli told Rai Sport ahead of Friday's Group B qualifier against Denmark.
Balotelli was selected for the squad after serving a three-match suspension for an aggressive outburst at the end of AC Milan's 2-1 defeat by Napoli last month, breaking Prandelli's player code of ethics.
"I'm convinced that Mario won't do anything out of the ordinary again and that he'll arrive at the World Cup well prepared," Prandelli said.
"I spoke to him and he said that was his dream. He needs to leave his problems behind and stop being the character that he's become."
Italy have already qualified for next year's World Cup in Brazil after winning Group B with two games to spare.
Balotelli will be rested for the Denmark match after picking up a thigh injury.