The controversial striker completed the formalities of the reported £20 million move from the Premier League champions after arriving on Wednesday and being swamped by reporters, photographers and fans.
Balotelli briefly spoke to the Milan Channel after landing at the city's Malpensa Airport, saying: "I'd wanted to play for Milan for such a long time. Obviously I played for other teams and couldn't come. But when there was the chance, I ran."
He told the City website of his feelings after completing the move: "I said goodbye to everyone at the meal in London before the game at Queens Park Rangers. It was a very emotional for me.
"I spoke with Roberto before I went to speak to the players. We spoke for some time about lots of things. He was sad, and I was too. But it was a good conversation. I love Roberto, he has been very important for my career, and I will always thank him for having trust and faith in me.
"Being at City was an important part of my life and career. I needed to grow up like a player and as a person and it has been a very good experience for me. I thank them for all of their support of me. Maybe one day we will see each other again."
Photographs have been published of the player wearing a Rossoneri scarf as he was presented with a team shirt bearing his name and his squad number 45, the same number he wore at first club Inter Milan and at City.
Milan vice-president and chief executive Adriano Galliani, who accompanied Balotelli on the flight from England, said: "I certainly do not have to introduce Mario Balotelli. It is a dream come true and something that we all wanted, with the president Silvio Berlusconi at the forefront.
"With the arrival of Mario, we have strengthened our team a lot. We have worked so hard and Mario has been in our hearts for a long time and finally we have succeeded in signing him."
Balotelli had been linked with Milan since the transfer window opened at the start of the month with both Galliani and Berlusconi regularly speaking about the player.
He departs City having won the FA Cup in 2011 and the league in 2012, as well as courting controversy on a regular basis.