And the Germany international reveals the first club he thought of was Arsenal as soon as he considered leaving Real after making a promise to Arsene Wenger three years earlier.
Ozil, 28, admits then-Real manager Jose Mourinho was shocked by his decision as he thought he wanted to end his career at the Santiago Bernabeu.
Mesut Ozil joined Arsenal for club-record £42.5m fee
Mesut Ozil called Arsene Wenger to force through Arsenal transfer
"I called a number that I'd saved in my phone back in 2010," Ozil wrote in his book Gunning for Greatness.
"'Mr Wenger,' I said, 'I promised that you'd be the first person I'd contact if I were ever looking for another club. Now I am.'
"Arsene Wenger told me that he had been keeping an eye on me the whole time and that he liked how I'd developed.
Jose Mourinho was shocked by Mesut Ozil's decision to leave Real Madrid for Arsenal Mesut Ozil distraught after Arsenal loss at Crystal Palace Mon, April 10, 2017
Click through the gallery for the snaps of Mesut Ozil after Arsenal's defeat at Crystal Palace
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Click to reveal the snaps of Mesut Ozil after Arsenal's defeat at Crystal Palace
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"And all of a sudden I had that positive feeling again, the one I'd had during our telephone conversation back in 2010.
"I sensed that this man, who I'd never met personally, had a very high opinion of me and trusted me. Exactly what I needed at this difficult time.
"Jose Mourinho was astonished. 'You didn't say anything to me. I thought you wanted to finish your career at Real Madrid,' he texted me."