Garnacho's future at Man United is uncertain after he criticised the team's performance and hinted at a possible departure following the Europa League final defeat to Tottenham Hotspur.
Several clubs including Aston Villa and Chelsea are monitoring Garnacho, with previous interest from Napoli failing due to price differences.
Bayer Leverkusen's new manager, Erik ten Hag, who previously gave Garnacho his breakthrough at Man United, is a big admirer of the player.
With multiple attackers expected to leave United, the club has signed Matheus Cunha and approached Bryan Mbeumo as they seek to overhaul their squad.