The Dutchman, who won a European Cup with Real in 1998 before triumphing twice with the Rossoneri, produced a perfect cross for Alexandre Pato to power in the late winner on Wednesday.
"We were in a difficult period and the win means we are getting better but it is not finished, this is just the beginning," the Dutchman told reporters after arriving back in Italy.
Milan, in their first season under rookie coach Leonardo, are only eighth in Serie A but showed a determination in last weekend's 2-1 win over AS Roma which had previously been lacking.
"We've got to build on these two important victories," added Seedorf.
They travel to Chievo on Sunday with goalkeeper Dida likely to keep his place, despite gifting Real their first goal, because Marco Storari and Christian Abbiati are injured.
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