The 25-year-old has already confirmed that he will leave Signal Iduna Park at the end of the season, and it has been reported he has already agreed to join Bayern Munich.
The Poland international has already confirmed he will part company with Die Schwarzgelben when his contract expires at the end of the season, and the 25-year-old stated Wednesday that he has already decided upon his next destination.
It has been repeatedly claimed that Lewandowski is bound for Bayern Munich and Mourinho sees no reason to question the veracity of those reports.
"I think his story is a book that was written a long time ago," the Portuguese told Sky Sport Germany ahead of his side's Champions League meeting with Schalke. "Everybody knows how the story ends. It surprised me that he was even associated with us. It's that obvious."
Lewandowski is in his fourth season at Dortmund since joining from Lech Poznan in 2010 and has scored 88 goals in 156 appearances for the club.