At the 2016 Summer Olympics in Rio, she won a bronze medal in the 100-meter butterfly with a time of 56.63. Vollmer also competed in the 4×100-meter freestyle relay the same night, in which she swam the third leg with a split of 53.18. The U.S. team of her, Simone Manuel, Abbey Weitzeil, and Katie Ledecky won silver with an American record time of 3:31.89. She also swam in the 4 x 100-meter medley relay, helping the US team win the gold medal. Her gold in the medley relay was the 1,000th gold medal for the US at the summer Olympics.