Milan, who lost their Italian league title to Juventus in May, are swelling their ranks having let several older players leave including Gennaro Gattuso, Alessandro Nesta, Filippo Inzaghi, Gianluca Zambrotta and Mark van Bommel.
Dutchman Seedorf, who triumphed in the 2003 and 2007 Champions League finals with Milan to notch up four winners' medals, has joined the band of departures but did not reveal where he is going amid reports he will join Brazil's Botafogo.
"I thank everyone, truly everyone. What emotion," the 36-year-old, a bit part player last term, told a news conference on Thursday.
"I will let you know soon about my future. I am taking my time. I have lots of offers," added the man who is giving his Milan number 10 shirt to Swedish striker Zlatan Ibrahimovic.
Massimiliano Allegri's side have drafted in Fiorentina's Riccardo Montolivo and Nancy's Bakaye Traore for next term but with Mathieu Flamini set to be released, another midfielder should arrive before the August kick-off.
Milan also said in a statement that midfielder Sulley Muntari had undergone surgery on knee ligament damage and is expected to be fit in five or six months.
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