The Brazil international will join the MLS club in January on a free transfer after AC Milan confirmed they have terminated his contract.
“Orlando City SC announced today it has signed global soccer icon Kaká to a multi-year contract,” read a statement from the Florida club on Tuesday.
“The signing marks yet another historic milestone in the Club’s journey to joining Major League Soccer starting in the 2015 season.”
Milan confirmed on Monday that the Ballon d’Or winner was leaving the club.
The MLS outfit also confirmed that the 32-year-old will return home to join first club Sao Paulo on loan for the Brasileirao 2014 season before joining up with his new club next year.
"I have said before that I wanted to play in America," he said. "It is a dream come true.
"MLS is growing so fast, I want to do my part to help to grow the sport in this country."
He joins the club for what will be their first season as a MLS club after being confirmed as an expansion club for the 2015 season.
Kaka becomes the second big name to move to USA this summer following David Villa's transfer to New York City from La Liga champions Atletico Madrid.