This paper discusses the biostratigraphy and palaeoecology of calcareous nannofossils of the uppermost Mozduran Formation in the Jozak section in west Kopet-Dagh basin. The Mozduran Formation consists of white to grey Limestone. In the studied sections, samples are taken and prepared with smear slides. In the Jozak section, 17 species have been determined. Based on nannoplanktons and as a result of biostratigraphy studies, the nannofossil standard zones (CC4) are identified. According to this zone, the age of the studied thickness is Early Hauterivian in this section in west Kopet-Dagh basin. The presence of warm water indicators (Nannoconus, Watznaueria, Lithraphidites) suggests warm surface water conditions in the studied thickness. In the Jozak section based on Nannoconus spp., low fertility conditions are suggested. The studied area is deposited in low to middle latitudes and shallow marine environments.