Leyva has a sister, Dayanis Mesa, who is a television host. His stepfather and coach, Yin Alvarez and mother, Maria Gonzalez, were both members of Cuba's national gymnastics team. Gonzalez and Leyva defected to Miami when Leyva was two years old. Alvarez defected by swimming across the Rio Grande to the United States while his team was competing in Mexico. Together, Alvarez and Gonzalez opened a gym in Miami several years later, and they married in 2001. Leyva's biological father, Johan Leyva, lives in Spain.
Junior career
Leyva competed at his first Winter Cup in 2006. He went on to compete in the junior division of the US National Championships, where he came 1st all-around, won gold on floor exercise and horizontal bar, and tied for silver on parallel bars. In 2008, at the Junior National Championships, Leyva won the all-around, high bar, parallel bars, and pommel horse titles. He was also the horizontal bar champion at the 2008 Pan American Gymnastics Championships in Argentina. He went on to be chosen as part of the 2008 Pacific Rim Championships team and competed in San Jose, California. The US team won gold, and Leyva won gold in the all-around and bronze on parallel bars in the junior division finals.
Senior career
2009
In 2009, he became the youngest member of the U.S. senior national team at age 17, and at the National Championships won the gold medal on the horizontal bar and the silver medal on the parallel bars. He was chosen as one of 4 US male gymnasts to compete at the 2009 World Artistic Gymnastics Championships in London. He qualified to the horizontal bar final, where he placed 4th.
2010
After winning medals on his two best events at the Winter Cup, he was selected for the men's team to compete at the Pacific Rim Championships in Melbourne. He won individual titles on horizontal bar and parallel bars, as well as a bronze medal on still rings. He also qualified to the all-around and pommel horse finals, where he placed 7th in both events. In the summer he once again competed at the Visa Championships, where he became the U.S. gold medalist on the parallel bars and the all-around silver medalist. He was chosen for the team to compete at the 2010 World Artistic Gymnastics Championships. In Rotterdam, he contributed to the team's 4th-place finish and also qualified to the horizontal bar final, where he placed in 5th.
2011
At the Visa Championships in Saint Paul, Leyva beat reigning national champion and world bronze medalist Jonathan Horton in the all-around, winning his first all-around US National Championship at the senior level. He also won the parallel bars and horizontal bar titles. He was subsequently chosen to be one of the anchors for the U.S. team at the 2011 World Artistic Gymnastics Championships in Tokyo, which won the bronze medal. This was the first time the U.S. men's team had won medals at Worlds since 2003. Leyva qualified to the all-around final, but his chin crashed into the horizontal bar in his last rotation, and he was unable to complete his routine. He scored only 6.466, resulting in a 24th-place finish. He rallied for event finals, where he won gold on parallel bars.
2012
Leyva won medals on several events at the Winter Cup, then won the American Cup in New York City. He placed 2nd in the all-around at the National Championships in Saint Louis, behind John Orozco. He defended his national titles on parallel bars and horizontal bar. He went on to compete in the Olympic Trials in San Jose, where he came first with his combined scores from Visa Championships and the two days of Trials. This secured him an automatic berth onto the U.S. Olympic Team with Orozco, who finished in second place overall. The next day, it was announced that Leyva and Orozco would be joined in London by Jonathan Horton, Sam Mikulak and Jake Dalton, with their 2011 Worlds teammates Alex Naddour, Steven Legendre and Chris Brooks as alternates. Leyva earned the bronze medal in the individual all-around at the Olympics.
2016
Leyva, originally an alternate, was added to the 2016 U.S. Olympic Team on July 15, 2016 following the withdrawal of John Orozco due to an ACL injury. On August 6, 2016 the men's team qualified for the team final in second place. Leyva qualified individually for individual event finals in both parallel bars and horizontal bar. He, along with his four other teammates, competed in the team final, where he contributed scores on pommel horse, parallel bars, and high bar. He had an unfortunate fall on high bar, and the team finished 5th once again. On August 16, Danell won silver in the Olympic men's parallel bar final with a score of 15.900. About an hour and a half later, he won another silver in the horizontal bar final, scoring 15.500. Despite being originally named as an alternate to the team, Leyva is the only member to walk away with two medals, contributing to the U.S. men's gymnastics team total of three medals, along with Alex Naddour's bronze on the pommel horse.
Sponsorships
In 2013, Danell signed a multi-year sponsorship agreement with Adidas Gymnastics. Fellow US Olympic Team members Jake Dalton, McKayla Maroney and Jordyn Wieber were also sponsored by Adidas.
