An Upper Devonian to (?)Lower Mississippian section at Hushoot Shiveetiin gol in the Baruunhuurai Terrane of the Central Asian Orogenic Belt (CAOB) was investigated. A generally well-preserved and diverse ostracod fauna was collected from the Late Devonian (Famennian) Samnuuruul Formation in western Mongolia. It is the first rich assemblage described from this area. The ostracod fauna consists of 19 genera and 25 species. Two of the species are proposed new species, and 13 species are described in open nomenclature. The Mongolian ostracod fauna is similar to coeval faunas in western China and Laurussia, but also contains new, endemic species. Two new taxa are described: Beyrichiopsis hushootensis and Ampuloides beckeri. Ostracod findings are characterized by the Eifelian Mega-Assemblage (I-III) representing a nearshore, variable palaeoenvironment which is in accordance with facies analysis provided by other studies.