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. 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 raced to fifth place by a hundredth of a second (0.01) behind Pini in a time of 52.69 seconds. Chang failed to advance into the semifinals, as he placed twenty-sixth overall in the preliminary heats.