Lamecha Girma initially started over medium distance distances before a former coach suggested that he focus on the obstacle course due to his height. In order to increase his chances of reaching the top of the Ethiopian team, he therefore moved to the capital Addis Ababa. First appeared in 2018 at the age of 17 at the U20 championships in his home country. There he was able to achieve 5th place over a 3000 m obstacle in 8: 46.23 minutes. In spring 2019 he also competed in this discipline at the U20 African Championships in Abidjan. There he won the bronze medal in 8: 48.56 minutes.
In October he competed at the World Championships in Doha. He won the last of a total of three heats. In the final, he had a tough race with the defending champion and top favorite Conseslus Kipruto and had to admit defeat in the finish sprint with a gap of one hundredth of a second. With this runner-up world title, he almost managed to end the long-standing dominance of the Kenyans on this route, he also set a new national record in 8: 01.36 minutes and also set the third fastest time over this distance in the U20 age group at this point in time.
His international breakthrough in 2019 earned him the Rising Star Award at the World Athletics Awards. At the beginning of 2020 he competed in an international cross-country race for the first time .