The Dane has signed a two-year deal in what will be his first job in club football since 2019.
He is expected to have his first training day at Bayer Leverkusen on Wednesday and will be in charge of his new club for the first time on Friday when the opponent at home will be Frankfurt.
“I’ve always perceived Bayer 04 as a very well-run, highly structured, and ambitious club," said Hjulmand. "That impression has been confirmed in recent days. It’s an honour to be entrusted with such a team.
"The task motivates me greatly - to shape the future of Bayer 04 Leverkusen with both proven and exciting new players, following the club’s outstanding successes in the past.”
Bayer Leverkusen needed a new coach after Erik ten Hag was fired after just three official games in charge last Monday.
Ten Hag joined the former Bundesliga champions this summer after being out of a job since November 2024, when the former Ajax boss was fired by Manchester United.
Bayer Leverkusen won three of their five games in pre-season and started their official campaign off with a win over Grossaspach in the DFB Pokal, but got off to a bad start in the Bundesliga with a 2-1 home loss against Hoffenheim and 3-3 draw with 10-man Werder Bremen.
“We’re very pleased about the appointment of Kasper Hjulmand, whose work we’ve followed closely over a long period," said Leverkusen's sporting director Simon Rolfes.
"His assistant coach with Denmark, Ismael Camenforte, was also active with us for several years. Kasper personally recommended him to us back then. His training methodology is therefore well known within our club, and Kasper himself is familiar with Bayer 04 from recent years.
"He will now work with our team to re-establish a clear and dominant playing style. Kasper is the right person to develop our new Werkself into a top team again - one that will pursue the most ambitious national and international goals.”