 On 30 August 2013, Milan announced that Boateng had been transferred to German Bundesliga club Schalke 04 for a €10 million transfer fee on a four-year contract due to expire in June 2017.Boateng made his debut for Schalke 04 in a 2–0 victory against Bayer Leverkusen.On 14 September 2013, he scored the winning goal for Schalke 04 in a 1–0 win over Mainz 05.