Erlein, 18, joins Leverkusen on a four-year deal, but will spend the 2026/27 season furthering his experience in Bundesliga 2.
Having previously won the U19 Bundesliga with Hoffenheim, the right-back impressed for the reserves last term, registering five assists in 31 3. Liga outings. The Germany youth international - who was part of the team that lost the UEFA EURO U19 2026 final to Spain on 11 July - made his sole senior appearance to date in the 2024/25 UEFA Europa League.
Leverkusen sporting director Simon Rolfes said the club view Erlein as a promising prospect. "Luca is a highly talented, intelligent and robust defender. We're delighted to have completed this transfer."