Brazilian playmaker Kaka, the 2007 world player of the year, was named captain of Orlando City, the club announced.
The franchise will make its Major League Soccer debut when they play host to fellow MLS expansion newcomer New York City FC on March 8 at the Citrus Bowl.
"Kaka has demonstrated great leadership both on the field and in the locker room since the start, and the other players have naturally looked to his guidance throughout pre-season, so he was the natural pick to skipper the club," Orlando coach Adrian Heath said.
The 32-year-old played for AC Milan from 2003 to 2009 and again last season after a four-year stint at Real Madrid. He was a World Cup winner with Brazil in 2002 and won the Champions League with Milan in 2007 as well as the Spanish title with Real in 2012 among other honours.
Orlando City have also signed central defender Seb Hines, on loan, from English Championship side Middlesbrough with an option to extend the deal.
The 26-year-old former England youth international has scored four goals in 100 matches for Middlesbrough and has had loan spells at fellow English clubs Oldham and Coventry City.
"We're very pleased to have Seb join us," Heath said. "His experience will be very valuable for our team's competitive position in our first MLS season."