Confidence in the Italy camp is low as a result of their pre-tournament preparations, drawing with Ireland and Luxemburg and failing to convince despite beating Brazilian club side Fluminese 5-3.
However, the Real Madrid coach urged the four-time World Cup winners to pull in the same direction and take inspiration from his Madrid side that won the Champions League last season.
"When you take part in a World Cup there is always a lot of excitement and tension and everyone needs to chip in if you want to achieve something big," said Ancelotti in a letter published in La Gazzetta dello Sport.
"However, people are sceptical about our chances, and do not believe in us. Well, I can guarantee that if the team and the coaching staff stay united and all read from the same page, then the atmosphere will become more favourable, and results are more likely to go our way.
"That is how Real Madrid won the Champions League. That's why now it's important to encourage Italians to get behind our lads."
The Italian admitted that Prandelli's side are far from being the tournament favourites, but also pointed out Italy were unfancied before the victorious World Cups of 1982 and 2006.
Italy begin their campaign against England in the stifling conditions of Amazonian city Manaus, before facing Costa Rica and then Uruguay.
"We are in a difficult group," admitted Ancelotti, "but our opponents should be worried about our presence in it. One thing is for certain, facing Italy is difficult for every team. We are a strong team tactically, we are experienced and we have players that can make the difference."