She is the first Brazilian woman to win three Olympic medals in an individual sport, being the best female judoka in the history of Brazil.

[6] When she was still 15 years old, she competed at 2007 Pan American Games in Rio de Janeiro and won a silver medal, losing in the final to future UFC champion Ronda Rousey.

[7][8] At the 2008 Pan American Judo Championships held in Miami, she became champion of this competition for the first time, obtaining the gold medal.

[9] In 2008, Aguiar competed at Olympic Games in Beijing but lost her only match with Spanish judoka Leire Iglesias.

[12] After spending ten months away from the mat due to knee surgery, in October 2009, Aguiar won the bronze medal in the 78 kg category at the 2009 World Judo Juniors Championships in Paris.

[13] In 2010, after the injury, Aguiar changed category from middleweight to half-heavyweight[14] and won a gold medal at 2010 Pan American Championships in El Salvador.

At the 2010 Judo Grand Slam Rio de Janeiro (Grand Slam is the tournament that gives the most points in the judo ranking after the Olympic Games, the World Championships and the World Masters), she defeated the French number 1 in the ‍–‍78 kg category, Celine Lebrun, and reached the bronze medal.

[15] In September of that same year, she participated at the 2010 World Championships and lost the final to Kayla Harrison from the United States, receiving the silver medal.

[16] By winning gold at the 2010 World Judo Juniors Championships in Agadir, Mayra became the athlete with the most medals in the competition of all time.

[20] She won gold at the 2011 Judo Grand Slam Rio de Janeiro defeating Kayla Harrison.

[31] At the 2013 World Judo Championships, held in Rio de Janeiro, she obtained a bronze in her ‍–‍78 kg category and a silver with the Brazilian women's team.

[32][33] After the 2013 World Championships, she only returned to competition in July 2014, at the 2014 Judo Grand Slam Tyumen, where she won four matches and secured the gold medal, defeating her rival Kayla Harrison.

[35] Aguiar didn't fight for 8 months after winning the world title, until she entered the 2015 Pan American Judo Championships and became five-time champion of the tournament.

[38] In February 2016, Aguiar won the gold medal at the 2016 Judo Grand Slam Paris, becoming two-time champion of this tournament and defeating the American Kayla Harrison, her biggest rival in the category, by ippon in the final.

[56] In 2021, Aguiar won one of the bronze medals in the women's 78 kg event at the 2020 Summer Olympics in Tokyo, Japan.

The only Brazilian champion in Japan until then was Sergio Pessoa, who won the Jigoro Kano Cup in 1986, in a different format than the current one.