Lee is the 2020 Olympic all-around champion and uneven bars bronze medalist, the 2019 world championship silver medalist on the floor and bronze medalist on uneven bars. She was a member of the teams that won gold at the 2019 World Championships and silver at the 2020 Summer Olympics.
She is a six-time member of the U.S. women's national gymnastics team, and with six world championship and Olympic medals, she is tied with Gabby Douglas, Kim Zmeskal, Kyla Ross, and Rebecca Bross as the tenth-most-decorated American female gymnast.
Lee has received numerous honors and awards. In 2021, she was named Female Athlete of the Year by Sports Illustrated, named Sportswoman of the Year by the Women's Sports Foundation, and included in Time 100, Time's annual list of the 100 most influential people in the world. She also received an Asia Game Changer Award.
As a result of the ongoing COVID-19 pandemic, the 2020 Olympic Games in Tokyo, originally scheduled to take place in the summer of 2020, were postponed to July 23-August 8, 2021. Lee competed on all four events during qualifications with the U.S. advancing to the team final in second place behind the Russian Olympic Committee. Lee finished third overall behind Simone Biles and Rebeca Andrade and qualified for the individual all-around final. She progressed to the uneven bars final in second place behind Nina Derwael and the balance beam final in third behind Guan Chenchen and Tang Xijing.
Lee was initially only set to compete on uneven bars and balance beam in the team final, but when Biles withdrew from the competition after the first rotation, Lee replaced her on floor exercise. She hit all three of her routines and scored 15.400 on bars and 14.133 on beam. The U.S. won the silver medal behind The Russian Olympic Committee. In the all-around final, Lee posted a score of 14.600 on the vault, 15.300 on the uneven bars, 13.833 on beam and 13.700 on floor, leading all competitors with a 57.433 total overall. She won the women's individual all-around gold ahead of Brazil's Rebeca Andrade and Angelina Melnikova of the Russian Olympic Committee. Lee is the sixth U.S. woman to claim the Olympic all-around title following Mary Lou Retton, Carly Patterson, Nastia Liukin, Gabby Douglas, and Simone Biles. She is also the first Hmong-American Olympian, the first Asian American woman to take the Olympic all-around crown, and was reported to be the first all-around Asian champion of any nationality. Lee was the first competitor in the starting order in the uneven bars final and uncharacteristically failed to connect several elements. She scored 14.500 and captured the bronze. She received a score of 13.866 in the balance beam final and placed fifth after a large balance check on one of her elements.
Lee registered for classes at Auburn University in August 2021 and left elite gymnastics to compete in the NCAA. Lee made her NCAA debut on January 7, 2022, in a tri-meet against North Carolina and Bowling Green. She competed on uneven bars and balance beam to help Auburn secure the win. A week later, Lee debuted her floor exercise routine in a meet against Arkansas. She made her all-around debut for Auburn on January 28 in a matchup with Alabama. Auburn won the meet with Lee winning the all-around title outright with a total score of 39.700. She shared the individual bars and beam titles. As a result, Lee was named SEC freshman of the week for the first time. On February 5, Lee earned her first collegiate perfect ten on the uneven bars in a meet against LSU. She was only the sixth Auburn gymnast to score a perfect ten and the first since 2004. Lee also won the all-around with a score of 39.825. On February 25, in a meet against Kentucky, Lee earned her first perfect ten on the balance beam and became the first collegiate gymnast to perform a Nabieva on the uneven bars. At the NCAA Championship, Lee finished first on balance beam and second in the all-around behind Trinity Thomas. In March 2023 Lee was diagnosed with an unspecified rare kidney condition for which there is no cure. On April 3 Lee announced that she would end her sophomore season early due to her health issues, thus concluding her NCAA gymnastics career.
