In present paper we supplement and summarize morphological data and taxonomical status of Rodentoxyuris sciuri — a parasite of red squirrel for the first time reported from Poland. Based on molecular data, we made an attempt to find the phylogenetic position of this nematode. Eight individual of squirrels collected from different parts of the city of Wroclaw (Lower Silesia, SW Poland) were subject to standard helminthological dissection. The helminthfauna of Sciurus vulgaris was represented by R. sciuri only, with the prevalence amounting to 100% (all eight individuals were infected) and a mean intensity of infection of 184.13. As a result of sequencing a partial sequence of 18S rDNA was obtained; and the phylogenetic relationships between analyzed species are discussed.