The North Anatolian Fault Zone (NAFZ) forms the boundary between the Anatolian and Eurasian plates and hosts many tectonic basins. The chronology of the NAFZ basin deposits is established mostly by pollen and partly by mammalian fauna studies. Nonetheless, the formation history of these basins starting in the Late Miocene to the Pleistocene and actively continuing today is still incompletely known because biochronological data are still scarce. A new micromammalian faunal assemblage from four horizons at the Umurlu locality (Niksar Basin, Tokat-Turkey) has been investigated; it improves our knowledge about the chronology of this basin infill. The recorded species are Mesocricetus cf. brandti, Cricetulus migratorius, Arvicola cf. mosbachensis, Microtus arvalis, the first fossil form of M. (Terricola) subterranean from Anatolia, Clethrionomys cf. glareolus, Apodemus flavicollis and Nannospalax cf. xanthodon. According to the stratigraphic range of these species the age of the deposit is constrained between early Middle Pleistocene and Late Pleistocene (i.e., 480-130 ka). The fossil assemblage indicates a mixture of open environments with meadows and grasslands associated with forested and bushy vegetation covers. This fauna and the implied environment are typical for an interglacial period, most probably within the interval of MIS 12-5. The studied rodent assemblage with elements of several palaeobiogeographic affinities shows once more the key position of Anatolia as a bridge between the Old World continents. It improves our knowledge on Quaternary micromammals of Anatolia, which is still poorly documented, and provides a well-constrained age of the locality.