Elliot Giles first took part in national competitions in 2011 over the middle distance 800 and 1500 meters. In August he ran over 800 meters of the season's best in 1: 53.24 minutes in Birmingham. In the following years he could not contest any competitions due to injuries. In July 2014, he was involved in a motorcycle accident in Birmingham that almost marked the end of his career. Although he did not break any bones from the accident, he sustained severe head and back injuries. In 2015 he was able to compete again. Throughout the year he continuously improved his time over 800 meters up to 1: 47.55 min in July. In June he finished fourth in the British U23 championships. In May 2016 he ran a new best time in Watford in 1: 47.21 minutes. Then he was the first time British champion over 800 meters. A month later he took part in the European Championships in Amsterdam. After he survived the preliminary and semi-finals, he increased to 1: 45.54 min in the final and won the bronze medal. In doing so, he also met the norm for the Summer Olympics in Rio de Janeiro. In his prelim, he finished seventh and was eliminated.
In the spring of 2017, Giles won the British 1500 meter indoor championships and was able to defend his 800 meter title at the national championships in July. Also in July he ran a time of 1: 44.99 minutes in London, the personal best. A month later he started at the same location at the World Championships . As the third of his prelim, he went one round, but was eliminated in the following semi-finals. Overall, he finished 20th. In 2018 he first took part in the World Indoor Championships in his hometown. In the run-up, he set a personal indoor best performance over 800 meters in 1: 45.46 minutes, with which he moved into the final. He could not build on his lead time and finished fourth in 1: 48.22 minutes. In February, Giles won the national indoor title for the first time in the 800 meters. At the Commonwealth Games in April in the Australian Gold Coast, he finished 15th over 800 meters. In the summer, the third victory in a row at the British Championships over 800 meters followed. After this success, he finally entered the European Championships in Berlin in August . He moved into the semi-finals, but was eliminated in seventh place. In February 2019, Giles set his indoor best time over 1500 meters in 3: 39.53 minutes. Over this distance he then competed at the European Indoor Championships in Glasgow. As fourth of his prelim, he missed the finals. In the summer he was fourth in the national championships over 800 meters. Then he went to the World Championships in Doha. He won the last of a total of six preliminary heats, then missed the finals as fifth in his semifinals in 1: 45.15 minutes, his second fastest time in 2019. Since his run was the fastest, he was ninth overall, as nobody from the other two semi-finals was faster than him.
Giles has been mentored by Jon Bigg since 2017. He lives in London, where he studied at St Mary's University , in the south-west of the city, and starts for the Birchfield Harriers from his native Birmingham.