Choo, who has been City's general manager since June, will take on the new role with immediate effect.
City chairman Mehmet Dalman said: "I would like to congratulate Ken on his appointment.
"Ken has brought stability and structure to Cardiff City over the last six months, allowing the club to plan for the future.
"His appointment as CEO is a recognition of his work and outlines our confidence in Ken's abilities."
#CardiffCity is pleased to announce the appointment of Ken Choo as Chief Executive Officer >> http://t.co/Ek3p2hoHoT pic.twitter.com/gcyNWg8dFp
— Cardiff City FC (@CardiffCityFC) November 10, 2014