Carlos Mayo first competed in Spanish championships in 2012. In the spring he started at the U18 indoor championships over 3000 meters, in which he finished third. In 2013 he was promoted to the U20 age group, in which he again competed a year later at the U20 World Championships in Eugene over 5000 and over 10000 meters. Over 5000 meters, he finished 14th, over which he was the Spanish U20 champion the same month before. He also made it into the finals over 10,000 meters and took tenth place there. In 2015, at the age of 19, he competed over 5000 meters at the U23 European Championships in Tallinn, where he won the bronze medal in 13: 55.19 minutes.
In 2016 Mayo started over 5000 meters at the European Championships in Amsterdam, where he finished 14th. In spring 2017 he competed at the European Indoor Championships in Belgrade over 3000 meters. He moved into the final where he finished eighth in 8: 06.15 minutes. In the summer he started again at the U23 European Championships , this time in Bydgoszcz, Poland. Over the 10,000 meters he won the gold medal in 29: 28.06 minutes and thus celebrated his greatest sporting success to date. Two days later he also secured the bronze medal over the 5000 meters. In 2018 he missed the entire season after just one competition in February. In 2019, he began to take part in regional competitions again and in December he competed at the European Cross Country Championships in Lisbon, where he finished 14th in the adult race.
Spain
Eugene
Tallinn
Amsterdam
Belgrade
Bydgoszcz
Lisbon