[1][2] In 2010, Chang edged out South Africa's Chad le Clos by 0.18 of a second to claim a gold medal in the 100 m butterfly at the first ever Summer Youth Olympics in Singapore, posting his personal best of 53.13.

[3] He also won a silver medal, as a member of the South Korean swimming team, in the men's medley relay at the 2010 Asian Games in Guangzhou, China.

Chang qualified for the men's 100 m butterfly at the 2012 Summer Olympics in London, by eclipsing a FINA B-standard entry time of 52.45 seconds.

[4] He challenged seven other swimmers on the third heat, including five-time Olympian Peter Mankoč of Slovenia, freestyle relay champion Clement Lefert of France, and former Olympic finalist Ryan Pini of Papua New Guinea.

Chang failed to advance into the semifinals, as he placed twenty-sixth overall in the preliminary heats.