Demirbay, who joined Hoffenheim from Hamburg in 2016, has scored four Bundesliga goals for Julian Nagelsmann's side this term, providing eight assists, and has signed a five-year deal with Leverkusen for a fee reported to be around €28 million (£24m/$31m).
The news that Leverkusen have bolstered their midfield contingent may, however, cast further doubt over Julian Brandt's future, with Liverpool, Borussia Dortmund and Bayern Munich all reportedly interested in the 23-year-old, while Kai Havertz has also been linked with a move away.
Demirbay had been mooted as a target for other sides across Europe.
His creativity will, however, be staying in the German top-flight.
"This is the next chapter after three great years at Hoffenheim," Demirbay told Leverkusen's official website.
"Leverkusen play really attractive attacking football. Their style suits mine and I’m really looking forward to becoming a part of this team."
‼️ TRANSFER NEWS ‼️— Bayer 04 Leverkusen (@bayer04_en) May 9, 2019
Kerem Demirbay will join us this summer from Hoffenheim with a contract until 2024!
We look forward to welcoming you to Leverkusen, Kerem! pic.twitter.com/8QjoYdsN3G
Germany international Demirbay will officially join Leverkusen at the end of the campaign, and will wear the number 26 shirt.
Demirbay made five appearances for Hoffenheim in the Champions League this season, and could well find himself back in Europe's elite club competition next term, with Leverkusen - who sit fifth in the Bundesliga - pushing for the final qualification spot.
“This is a clear sign of our ambition,” said Leverkusen sporting director Rudi Voller.
“We have a lot planned for the coming season but first we want to qualify for Europe. If we do that. We’ll need quality players like Kerem Demirbay.”