At the 2004 Athens Olympics she won a gold medal as a member of the winning United States team in the 4×200m freestyle relay that set the world record in the event. At the 2008 Beijing Olympics, she won the 100m butterfly in a world and Olympic record.
Vollmer has won a total of 28 medals in major international competitions, including 16 gold, 8 silver, and 4 bronze spanning the Olympics, the World Championships, the Pan American Games, the Pan Pacific Swimming Championships, and the Goodwill Games.
Vollmer was born in Syracuse, New York and raised in the Dallas-Fort Worth suburb of Granbury, Texas. As a child, Vollmer swam for coach Ron Forrest at the Fort Worth Area Swim Team (FAST).\
In 2003, Vollmer underwent heart surgery to correct a condition called Supra Ventricular Tachyardia, which produces a quickened pulse rate of about 240 beats per minute. Nonetheless, her heart conditions demand that a defibrillator be kept poolside when she swims as a precautionary measure.
Vollmer is married to Andy Grant, a former Stanford swimmer.
At age 12, she was the youngest swimmer competing at the 2000 U.S. Olympic Trials; she failed to make the team. She was also the youngest competitor to swim at the 2001 Goodwill Games.
2004 Summer Olympic Games
At the 2004 Athens Olympics, she was a member of the United States' gold medal winning 4x200m freestyle relay team that set a world record.
At the 2007 World Swimming Championships, Vollmer won a gold medal in the 4x200m freestyle relay. She also won silver in the 4x100m freestyle and the 4x100m medley relays.
She also participated in the 2008 Fiji Swims 18km relay in Fiji.
In 2009, she set her first individual American record, breaking Natalie Coughlin's 200-yard freestyle record with a time of 1:41.53.
At the 2009 World Swimming Championships in Rome, Vollmer won two medals a silver and a bronze. In the 200-meter freestyle, Vollmer set an American record in the semifinals with a time of 1:55.29. In the final of the 200-meter freestyle, Vollmer placed third and her American record was broken by Allison Schmitt. In the 4x200m freestyle relay, Vollmer swam the lead-off leg in 1:55.29. The American team finished in second place behind China with a time of 7:42.56.
At the 2011 World Swimming Championships in Shanghai, Vollmer won a total of three medals, two golds and one silver. In her first event, the 4×100m freestyle relay, Vollmer won a silver medal with Natalie Coughlin, Jessica Hardy, and Missy Franklin. Vollmer won gold in the final with a time of 56.87. In the 4×100m medley relay, Vollmer won gold with Natalie Coughlin, Rebecca Soni, and Missy Franklin with a time of 3:52.36. Swimming the butterfly leg, Vollmer had a split of 55.74. The final time of 3:52.36 for the medley relay was the second-fastest effort of all time, just behind the Chinese owned world record of 3:52.19.
2012 London Olympic Games
In London, she again broke her American record and set an Olympic record with a time of 56.25 in her 100m butterfly qualifying heat.