The 21-year-old is vying for a place in Cesare Prandelli's starting XI for the Euro 2012 quarter-final against England on Sunday after finding the back of the net in the Azzurri's final group game against Republic of Ireland.
Vieira played alongside Balotelli during his spell at Inter before linking up with the forward again at Manchester City, and the former Arsenal midfielder believes the Italian must now show that he has grown up.
"Mario will be 22 in August and he has now reached the point in his life and his career where he has to learn from his mistakes and show that he is a man and no longer a boy," Vieira told The Daily Telegraph.
"People will lose patience with you and get tired of helping if you do not improve your conduct or fail to learn from your mistakes.
"I think it can sometimes be difficult for Mario to accept criticism because, when people tell you that you are going to be the best, it can be hard to understand when you are on the wrong side of the critics.
"But I really feel that Mario is ready to accept help, however, and Mancini is also prepared to support him."
Balotelli's career at the Etihad Stadium looked in jeopardy towards the end of last season following a red card in a key game against Arsenal, but Mancini stuck by his countryman, something Vieira was glad to see.
"Whether Mario stays at City is something only he and Roberto can decide, but I really hope that he does because he is a player with fantastic potential and somebody who has already proved his ability to score important goals for the team.
"I think we have also seen that Mario has the potential to be a leader and somebody with real character.
"Just watch him when he takes a penalty. He is so cool in that situation, but having the confidence to take the ball and put it on the penalty spot shows he is prepared to take responsibility and display leadership."
And the Euro 2000 winner believes Balotelli should start the Euro 2012 quarter-final against the Three Lions, adding: "I certainly believe that he should start.
"He had a good chance against Spain which he should have scored and then had another game without scoring against Croatia, but in both games, he worked hard for his team.
"Prandelli must decide whether to start Mario against England, but I think that his strengths ensure that he would make it difficult for John Terry and Joleon Lescott."
England and Italy kick off at 20:45CET on Sunday.