The Brazil international joined Madrid for around £56million from AC Milan in 2009 but has found first-team opportunities limited during his time at the Bernabeu.
The 31-year-old has regularly been linked with a move away from the club but has previously preferred to try and fight for an opportunity with the Spanish giants.
However, the former winner of the Ballon d'Or and FIFA World Player of the Year award, now says he wants to leave.
Speaking after scoring twice for Madrid in Thursday's 4-0 win over Deportivo La Coruna in the Trofeo Teresa Herrera, Kaka said in AS: "I want to go.
"I think now is the right time for me and for the club to leave amicably. I've spoken with (Madrid coach Carlo) Ancelotti and with the club, they all know.
"My father is talking now with the club to try and resolve this situation.
"Things are now difficult for me in the team and the club know what I want. It's my obligation to work hard and continue training, but my father is already working to see if something comes up. I think that it's best for me and for the club."