Kaka agreed to contract terms with AC Milan on deadline day and reportedly accepted cutting his salary by more than half to rejoin his former club.
Following a free transfer from Real Madrid on Sunday, Milan announced on its website that the club reached a deal with the 2007 FIFA world player of the year early Monday.
Financial terms were not disclosed but the Gazzetta dello Sport reported that it's a two-year deal worth €4 million ($5.3 million US) per season plus bonuses — a significant drop from the €10 million ($13.2 million) Kaka earned with Madrid.
"Kaka made a big [sacrifice] to return here, showing a lot of affection for our shirt," Milan Vice-President Adriano Galliani said.
The 31-year-old Kaka wants to play for Brazil at next year's World Cup in his home country and should feature more at Milan.
"Milan is ideal for me," Kaka told Milan Channel. "I always find great champions here. Before there was Pippo Inzaghi now there's [Mario] Balotelli. I hope to experience great joys with Mario.
"I really want to play," Kaka added. "This is a special year for me because the World Cup is coming up but now I've got to do well with Milan. I was very sorry to leave but now it's even more special to come back."
With few other moves, Kaka's transfer was the highlight of deadline day in Italy. Other moves could involve three forwards, with Fabio Quagliarella of Juventus, Alberto Gilardino of Genoa and Marco Borriello of Roma each reportedly considering transfers.
Kaka joined Madrid from Milan in 2009 for €65 million ($92 million). But after injuring his left knee, he was never able to establish himself as a first-choice player in Spain.
Kaka did not play in an official match with Madrid after the recent arrival of Carlo Ancelotti, who coached him during his best seasons at Milan.
Kaka was the world's top player when he led Milan to the Champions League title in 2007, when he also helped the Rossoneri win the UEFA Super Cup and Club World Cup.
While he doesn't seem to be the player he once was, Kaka should still be an able replacement for Kevin-Prince Boateng, who transferred from Milan to Schalke last week. He could line up either in attack alongside Mario Balotelli or share playmaker duties with Riccardo Montolivo.