The 19-year-old Argentinian will join the 2024 Bundesliga champions to help replace Florian Wirtz, who has moved to Liverpool, as part of Erik ten Hag’s new-look team.
Leverkusen will not have an option to buy Echeverri, with the player set to return to Manchester City next summer.
City originally bought Echeverri from River Plate in January 2024, loaning him back to his previous club before he moved to Manchester in January this year.
The loan move comes as Pep Guardiola aims to operate with a smaller squad, despite Echeverri having recently made his debut and scored his first goal for City.