American midfielder Tillman joins Leverkusen from PSV
The 23-year-old attacking midfielder, who was born in Nuremberg, has signed a five-year deal until June 30, 2030.
The club has not given details of a transfer fee but media reports put it at 40 million euros ($47 million) which would equal the club record paid for Liverpool defender Jarell Quansah earlier this month.
Tillman joined PSV, initially on loan, from Bayern Munich in 2023 and last season scored 16 goals and provided five assists in 34 games for PSV.
"In Malik Tillman we have gained another player who has great ability and is very dangerous in front of goal," said Leverkusen sporting director Simon Rolfes.
"He can play in midfield either as a number 10 or as a number 8. Malik is an absolute top signing for us."
Tillman, who also spent a year on loan at Rangers in Scotland, won back-to-back titles in the Eredivisie but he now has his sights set on winning the Bundesliga.
"I want to win something. That was my aim in Glasgow and in Eindhoven and it remains my aim here," he said.
Tillman made 21 appearances for several Germany age-group teams before deciding to play for the USA in 2022, most recently in the Gold Cup final defeat by Mexico.