Tamirat won the Ethiopian national title in cross country in 2015 which led to his selection for the 2015 IAAF World Cross Country Championships. Making his international debut, he took sixth place in the senior race which helped the Ethiopians narrowly take the team title on equal points with Kenya (Muktar Edris, Hagos Gebrhiwet and Atsedu Tsegay were the other point-scoring team members). He had mixed fortunes in the rest of the season: he failed to finish the 2015 Berlin Marathon but set bests of 60:08 minutes for the half marathon and 27:22.64 minutes for the 10,000 metres.