Elymus sosnowskyi, a rare endemic species known from East Anatolia, Turkey, was first collected by D. Sosnowsky in 1912. After that it has been collected only one other time, by F. Sorger in 1981. During the "Taxonomic revision of tribe Triticeae in Turkey" project, which was supported by TUBITAK, E. sosnowskyi was recollected from 3 populations in Oltu and Narman (A8 Erzurum, Turkey) in 2007 and 2008. The present study aimed to provide detailed diagnostic characters of this rare endemic species, including its morphological, anatomical, and palynological features. Moreover, the amended and expanded description, distribution, phenology, and ecology of this rare species are provided, along with its conservation status.