The 73-year-old South Korean replaces Youssoupha Ndiaye of Senegal as head of the IOC's ethics commission.
Ban takes the job at a time as the IOC comes under fire again after its Brazilian honorary member Carlos Nuzman was arrested in connection with a corruption probe around the awarding of the 2016 Rio Games.
French authorities are also looking into payments around Tokyo's election to host the 2020 Games, and the dealing with the Russian doping affair has also tarnished the image of the IOC.
