At the 2017 World Championships in Athletics in London, he placed fifth in the men's 5000 m final in a time of 13:35.34; the race was won by his compatriot Muktar Edris.

In 2018, Selemon placed second over the 3,000 m at the World Indoor Championships in Birmingham, United Kingdom, clocking a time of 8:15.59 on 4 March.

On 31 August, Selemon set a world U20 record in the 5000 m at the Brussels Diamond League clocking a time of 12:43.02.

[4] Selemon competed in the senior men's race of the World Cross Country Championships in Aarhus, Denmark.

He headed back to Ethiopia, where on 26 December, he ran 1,500 m at the Ethiopian Clubs Competition in Addis Ababa, winning in 3:38.1.

He competed at several indoor track races in January and February, including a 7:26.10 3000 m, clocking him second place behind compatriot Getnet Wale.

[9] Selemon next raced at the Ethiopian Trials in Hengelo, where he won the 10,000 m in a time of 26:49.51 [10] holding off Yomif Kejelcha who was second, Berihu Aregawi placed third.

[11][12] Brutal humidity meant that the winning time of 27:43.22 was the slowest in an Olympic final since 1992, but Selemon's close was sublime as he ripped the last kilometer in 2:24.9 and last lap in 53.94.