The 27-year-old has joined the Bundesliga giants in a £10.5million deal.
“Negotiations were tougher than expected. I am happy to have Klaas-Jan. He will help us,” Schalke coach Felix Magath told the Bild newspaper on Tuesday.
The former Ajax star failed to make an impact at AC Milan since joining the club from Real Madrid last year.
Huntelaar told his official website: “It is true I never wanted to leave Milan but that changed when Zlatan Ibrahimovic came from Barcelona.”
