Abstract The paper presents morphological and ecological characteristics of Prestauroneis tumida Levkov recorded for the first time in Poland. The diatom Prestauroneis tumida Levkov was found in the microbenthos of the Czarna Staszowska River (left tributary of the Vistula River, south-eastern Poland). This diatom species was present in the upper section of the river (sampling sites: 1 – Drogowle, 2 – Raków) where saprobic state varied from oligosaprobic to beta-mesosaprobic. Dimensions of the valve were as follows: length 30-44 µm, width 8-11 µm and 13-16 striae in 10 µm. Our research updates the morphological diversity data such as measurements of valves in terms of width and the number of striae. The accompanying species of Prestauroneis tumida belonged to the group of good water quality indicators, from oligo- to mesosaprobic ones. Some of the identified species were indicators of alkaline, calcium-rich waters.