The 27-year-old had been available as a free agent since his contract with French Ligue 1 club Auxerre expired on June 30.
Mensah spent four years at Auxerre, helping the club win promotion to Ligue 1 and then survive in France’s top flight in each of his final two seasons.
He was a first-choice starter at left-back throughout that period and leaves the Stade Abbé-Deschamps as one of the club’s most reliable performers.
The Ghanaian had a wide range of options before choosing Koln. Fellow Bundesliga side FC Schalke 04, Coventry City in the English Premier League and a number of Turkish clubs all held discussions with his representatives in the days after his Auxerre contract lapsed.
Koln, who were seeking a direct replacement for Kristoffer Lund at left-back after the Denmark international returned to parent club Palermo at the end of his loan spell, ultimately closed the deal.
The move places Mensah into a select group. He becomes only the fifth Ghanaian to represent Köln in the club’s history, following in the footsteps of Anthony Baffoe, Edward Sarpei, Derek Boateng and Kingsley Schindler.
His arrival is part of a broader summer rebuild at RheinEnergieSTADION, with head coach Lukas Kwasniok’s side targeting a more competitive 2026/27 Bundesliga campaign after finishing 14th on their return to the top flight last season.
Mensah joins his new club fresh off an impressive World Cup with Ghana. He played every minute of all four Black Stars matches at the tournament.
He is expected to join the Koln squad for pre-season training in the coming days.
Follow all the transfer news LIVE this summer.
