Kaka swapped Milan for Madrid in a €65million deal in 2009 but the Brazilian has struggled to make the same impact in three years at the Bernabeu.
Robinho, who is a former Real star himself, admits he would be delighted if his international team-mate came back to Serie A.
“I would be very happy if Kaka returned to Milan,” Robinho told Marca.
“We are team-mates with the national team and we could achieve a lot together, especially now that both of us want to get ready for the 2014 World Cup.”
Brazil host the World Cup in two years’ time and Robinho, 28, and Kaka, 30, both retain ambitions of being involved.