Event Format: Swimmers competed in preliminary heats, semifinals and final. In the preliminary heats the swimmers with the best official starting times were placed in the last three heats. The 16 swimmers with the best time in the preliminary heats advanced to the semifinals. From the semifinals the eight swimmers with the best time in the semifinals advanced to the final.
Event facts: Men's 100 m butterfly competition was held at the National Aquatics Center and 65 athletes participated in the event.