The 20-year-old leaves Leverkusen after signing a five-year contract, which binds him to Mainz until June 2021, reports Xinhua.
"Levin Oeztunali is a highly gifted and versatile attacking midfielder who has already underlined his qualities in Leverkusen and Bremen," Mainz sporting director Rouwen Schroeder said on Thursday.
"We are pleased that we increase the quality of our squad with him."
The new arrival joined Leverkusen in July 2013 to make 14 appearances before he switched to Werder Bremen, where he played since January 2015 to score two goals in 41 matches.
"Mainz is the right club for the next step in my career," Oeztunali said.
"Mainz's style of play is aggressive and always offensively minded, which fits me well. I want to play with the team as soon as possible to help the club on the pitch."
Mainz play against Borussia Dortmund in the first round of Bundesliga on Saturday.
This website uses cookies.