at the
DecaNation meet in 2014 Castlin turned professional after leaving Virginia Tech, gaining an Adidas sponsorship, and set a season's best of 12.83 seconds at the
2011 USA Outdoor Track and Field Championships. However, she false started in the semi-finals and was disqualified. She secured her first national title at the
2012 USA Indoor Track and Field Championships, setting a personal record of 7.84 seconds in the process. The time ultimately ranked as the second fastest in the world that year for the 60 m hurdles. This gained her selection for the
2012 IAAF World Indoor Championships – her first senior appearance. In spite of her entering the competition as one of the favourites, she failed to finish her heat as she mistook the sound of the
starter's pistol for a recall (due to the echo in the hall) and stopped running before the first hurdle. At the
2012 United States Olympic Trials she reached the semi-finals, but her time of 12.93 seconds was not enough to progress. She performed well, however, on the
2012 IAAF Diamond League circuit that year. She greatly improved her personal record to 12.56 seconds as runner-up at the
Bislett Games in
Oslo – a time which ranked her sixth in the world for 2012. Her other major placings included fourth at both the
Meeting Areva in Paris and the
London Grand Prix. Castlin tried to defend her national title at the
2013 USA Indoor Track and Field Championships, but was beaten into second place by
Nia Ali. At the
2013 USA Outdoor Track and Field Championships she had her best national placing yet, taking sixth in a time of 12.61 seconds (her fastest that year). She ranked tenth globally for the season. Her 2013 was highlighted by a
world record in the infrequently contested
shuttle hurdle relay – at the
Florida Relays a team of Ali, Castlin,
Yvette Lewis and Queen Harrison completed the 4×100 m relay event in a new best time of 50.78 seconds. She ranked in the top three at the
2014 USA Indoor Track and Field Championships, doing so at the national event for the third year running. She was selected at the
USA Track & Field athlete of the week at the end of April 2014 as a result of her breaking
Brianna Rollins' streak of 35 races without defeat; Castlin's run of 12.571 seconds edged Rollins by five thousandths of a second and broke the
Drake Relays meet record. This proved to be her fastest of the season and enough to place her seventh in the annual global rankings. She defeated both Rollins (the world champion) and
Sally Pearson (the Olympic champion) at the
Spitzen Leichtathletik Luzern in July. She ended the year with a win in the non-Diamond League 100 m hurdles at the
Memorial Van Damme meet in Brussels. During the
2016 United States Olympic Trials for track and field, Castlin placed second in the 100 m hurdles with a time of 12.50 seconds, behind
Brianna Rollins and ahead of
Nia Ali, and qualified to represent the United States at the
2016 Summer Olympics in Brazil. She earned a bronze medal at the Rio Olympics in the 100 m hurdles, with a time of 12.61 seconds, outleaning Cindy Ofili at the finish. Castlin finished behind American teammates Brianna Rollins, who earned the gold medal with a time of 12.48 seconds, and Nia Ali, who earned the silver medal with a time of 12.59 seconds. It was the first time in Olympic history that American women had swept the medals in any event, and made the United States the first country to win gold, silver, and bronze in the women's 100 m hurdles in one Olympics. HSInternational Sports Management announced its signing of Kristi "Hollywood" Castlin, the
Rio Olympic Bronze Medalist at 100 m Hurdles. ==Personal bests==