"I have not chosen Real Madrid for money, but because it is the biggest club in the world. It is impossible to say no, for its sport and its history," said Sahin.
On meeting Mourinho, the youngster added: "I have spoken with Mourinho and he convinced me right away. We were a day together here in Dortmund and he convinced me very quickly.
"He is one of the best coaches in the world and I look forward to working with him. It is a challenge."