With Mourinho confirmed as the new manager at Old Trafford Friday after the sacking of Louis van Gaal
Monday, Ancelotti described the former Chelsea boss as "really smart."
The 53-year-old has been out of work since being axed by the Blues in December after the London club suffered a disastrous opening to its Premier League title defense.
Mourinho saw his team slump to nine defeats in the first 16 games and had a public falling-out with club doctor Eva Carneiro on the opening day of a volatile season.
But Ancelotti had no doubts that the Portuguese is the right man for Old Trafford.
Speaking the day before Mourinho's appointment, Ancelotti said: "I think a manager has to fit the style of the club -- and I think Mourinho is really smart, really clever and put a system in place of knowing the characteristic of the players."
"He won the Champions League at Inter Milan using a defensive style because they had really strong defensive players," " the 56-year-old Italian explained.
"At Real Madrid, he used attacking play because he had fantastic strikers."
Skeptics including United icon Eric Cantona have questioned whether Mourinho's often pragmatic approach would be suited to his new club's tradition of free-flowing football.
Cantona told the Guardian
: "I love Jose Mourinho, but in terms of the type of football he plays I don't think he is Manchester United.
"I love his personality, the passion he has for the game, his humor. He is very intelligent and, of course, he wins things. But I don't think it's the type of football that the fans of Manchester United will love, even if they win."
But Ancelotti disagreed, saying: "I don't think Mourinho is not good enough for the style of Manchester United -- I think he is really good for them because he has experience.
"He has won everything, and I think he is really good for Manchester United and also Manchester United for Mourinho -- he needs a top club like Manchester United."
Ancelotti, who has worked for some of the biggest clubs in world soccer, said he believes modern club owners can be divided into two types -- the fans and the financially-focused.
He said that while some owners were driven by a passion for the game, "the economic and financial aspect" of big business football was more important to others.
Asked which clubs focused more on finance, he said: "For example, Manchester United and Arsenal -- and other clubs, like AC Milan and Real Madrid, are more focused on the result."
Neither United nor Arsenal immediately responded to CNN's request for a comment.
Ancelotti -- whose prestigious roll-call of clubs includes AC Milan, Real, Juventus, Chelsea and Paris Saint-Germain -- takes over another of the game's biggest names, runaway German champion Bayern Munich, this summer.
He explained: "There is the owner that is really passionate because they are a fan, or the owner who has become passionate.
"For example, Roman Abramovich was not a supporter of Chelsea, but now he is a big fan and is really passionate.
"There are passionate owners like [Silvio] Berlusconi, who was born with Milan [as his club], and there are owners who are not so passionate.
"Maybe I can say -- and I didn't work with them -- that the owners of Manchester United think more of an economical aspect.
"There are clubs where the economic and financial aspect is more important than the result.
"Usually, the owners that are not so passionate are more focused on the financial aspect. The owners that are more passionate are focused on the result."