The 27-year-old is set to sign a three-year deal with Sparta Rotterdam after two years at Pittodrie.
Touzani struggled with injury during his spell with Jimmy Calderwood's side, making only 25 appearances and scoring one goal.
"Everyone at Pittodrie would like to wish Karim all the best for the future," read a statement on the club's official website.
Touzani, a product of the Ajax academy, played for Utrecht and Twente before joining Aberdeen in 2006.