Kaka was undoubtedly the headline arrival in the Italian top flight, as he ended a disappointing three-year spell in La Liga with Real Madrid in order to return to Milan.
"I'm coming home," he told Sky Italia after finalising his switch. 'I'm very happy and now I get to live lots of new joyous moments with Milan."
There was also a departure from the San Siro, with 18-year-old striker Andrea Petagna joining Sampdoria on a season-long loan with the option of co-ownership.
Sampdoria also acquired Birkir Bjarnason from Pescara on a permanent deal.
Hellas Verona enjoyed a successful end to the window, bringing in two highly rated loanees in the form of Juan Iturbe from Porto and Marco Donadel from Napoli.
Bologna and Catania were also busy in the loan market, signing Jonathan Cristaldo from Metalist Kharkiv and Jaroslav Plasil from Bordeaux respectively.
Meanwhile, young Inter midfielder Joel Obi will play his football for Parma this season, after agreeing a switch for the entirety of the 2013-14 campaign.
Juventus and Sassuolo were in negotiations for much of the day, as midfielder Luca Marrone joined the latter on a co-ownership deal while young striker Domenico Berardi joined the Serie A champions - though he will be loaned back immediately.
Serie A also saw a high-profile departure as goalkeeper Emiliano Viviano left Palermo to join Arsenal on loan for the season.
In other moves, Genoa captured Ricardo Centurion, Chievo Verona signed Tomasz Kupisz and Alessandro Bernardini and Livorno brought in Luca Anania.
