Choi qualified for the men's 200 m breaststroke at the 2012 Summer Olympics in London, by breaking a South Korean record and clearing a FINA A-standard time of 2:11.17 from the FINA World Championships in Shanghai, China. He challenged seven other swimmers on the third heat, including former silver medalist Dániel Gyurta of Hungary and local favorite Michael Jamieson of Great Britain. Choi raced to seventh place by less than 0.04 of a second behind Ukraine's Igor Borysik in 2:13.57. Choi failed to advance into the semifinals, as he placed twenty-fifth overall in the preliminary heats.