The paper documents Middle Miocene (Badenian) ostracods of the Polish part of the Western Carpathians for the first time. The material has been collected at the outcrop in the Kamienica Nawojowska locality, in the Nowy Sacz Basin. The ostracods allowed the identification of 42 species, referred to 26 genera and representing 15 families. Among them, a few species (e.g. Neonesidea cf. corpulenta (G.W. Müller, 1894), Pokornyella cf. devians Bonaduce, Ruggieri et Russo, 1986) and the genus Jonicythere Mostafawi, 1986, appear to be recorded from the Middle Miocene of the Central Paratethys for the first time. Some species show uncommonly high variability. Besides the ostracods, the associated remnants of green algae (Chlorophyta), assigned to three genera, are also preliminarily identified and illustrated. The taxonomic composition of ostracods, as well as their preservation state, and the associated green algae suggest their marine, shallow-water (inner neritic), rather highly dynamic and unstable environment. The close similarity of the recognized ostracod assemblage to those known from the Middle Miocene deposits of the others parts of the Central Paratethys (including the Carpathian Foredeep), Mediterranean areas, and the Atlantic border of Europe seems to be important. It suggests intensive exchange of fauna within these bioprovinces.