Victor Boniface broke the deadlock in the 51st minute, capitalizing on a rebound after Milan goalkeeper Mike Maignan initially saved Jeremie Frimpong’s shot.
As the match wore on, Milan gained momentum and came close to equalizing when Theo Hernandez’s deflected long-range strike hit the crossbar with seven minutes left. Spain’s Alvaro Morata then headed just wide on the follow-up.
Leverkusen were dominant for much of the match and had an earlier goal disallowed in the first half. Boniface found the net from a precise Frimpong cross in the 21st minute, but VAR ruled Frimpong offside.