In 2019, Boateng began a relationship with Polish-born model Kasia Lenhardt. In February 2021, following a public spat between the two after Lenhardt crashed Boateng's Mini Cooper and was charged with drunk-driving, Boateng announced the two were breaking up, stating, "We will go our separate ways from now on. That is regrettable, but for my family and for me it is the only right one." The pair's relationship had already become publicly sour, with Boateng accusing the model of sabotaging a previous relationship and blackmailing him to stay with her. On 10 February, one week after the confirmed breakup, Lenhardt was found dead in an apartment in Berlin, with investigators believing the cause of death to be suicide. Boateng, who was in Qatar playing in the FIFA Club World Cup with Bayern Munich at the time, was then confirmed to have departed the country due to personal reasons by the club.