The 28-year-old has signed a one year deal at the club and Bayer managing director Wolfgang Holzhauser revealed his delight at the capture."We have signed an experienced and high quality back-up for our number one Bernd Leno. We made this move as we are involved in three competitions," he told the club's official website.
Rensing brings with him vast Bundesliga experience having made over 50 appearances for Bayern during his seven year spell with the German giants.
And sporting director Rudi Voller was equally thrilled to bring a player of such pedigree to the BayArena.
"Michael Rensing was always a key player at Cologne and he produced some outstanding performances there. His experience can and will help Bernd Leno to perform even better in goal," he added.