The former Manchester United boss’s dismissal follows a troubled start to the league season, including a 2-1 home defeat and a draw against Werder Bremen where Leverkusen let a two-goal lead slip.
On-pitch disharmony, such as an argument over who would take a penalty, was publicly deemed "unacceptable" by Ten Hag.
The club faced challenges, including the departure of key players and reported friction between Ten Hag and the club's hierarchy.