In the 100-meter breaststroke heats, King finished 1st with a time of 1:05.78 and qualified for the semifinals. There she again finished first with a time of 1:05.70. The next fastest swimmer was Yuliya Yefimova from Russia, the reigning world champion who had previously served a 16-month doping suspension for failing a 2013 drug test. Yefimova also failed a drug test in 2016, but with no research on how long the drug stayed in a person's system, she was not banned or given a suspension. As King looked on from the ready room, where swimmers gather before they race, Yefimova won her semifinal and wagged her index finger. After posting the fastest time in the 100 m breaststroke semifinals, King expressed distaste. In a post-race interview with NBC, King said, "You wave your finger No. 1 and you’ve been caught drug cheating? I’m not a fan." King went on to win the Olympic gold medal in the 100-meter breaststroke, setting an Olympic record of 1:04.93 in the process.