In the evening of day six, Dressel tied the Olympic record in the 100 meter butterfly with a time of 50.39 in the prelims heats. This first Olympic record in the 100 meter butterfly Dressel set less than nine hours after setting the Olympic record in the 100 meter freestyle. In the second semifinal heat of the 100 meter butterfly on day seven, Dressel swam a 49.71 and broke the Olympic record of 50.31 Kristóf Milák set in the first semifinal heat. Later on day seven, Dressel swam three hundredths of a second off from setting a new Olympic record in the prelims of the 50 meter freestyle with his time of 21.32 and advanced to the semifinals ranked first.