After a successful one week trial, Mensah signed a two-year contract with the Danish club on 1 August 2014. After only two months in the club, Mensah signed a new contract again, this time until the summer 2017. Mensah had a good season for AC Horsens in the Danish 1st Division with 18 games played in the 2014/15 season. After two good seasons, Mensah suffered a broken shin injury, that kept him out for about 5–6 months in October 2016. However, he signed a contract extension just one month after his injury. He went back from the injury at the start of April 2017.