Abstract <p>For the first time, an analysis of the parasite and endosymbiont fauna of the larval forms of the moor frog (<i>Rana arvalis</i> Nilsson, 1842) at different stages of ontogenesis in natural and urban landscapes of the Middle Urals is presented. Six species of helminths of the phyla Nematoda and Platyhelminthes at different developmental stages and one species of endosymbiont (phylum Bigyra) were found. The greatest infestation of <i>R. arvalis</i> tadpoles and juveniles with the intestinal trematode <i>O. ranae</i> of different age groups was noted. Nematodes were found in metamorphosed amphibians. Along the urbanization gradient, parasite communities in tadpoles and froglets become simplified, which is likely associated not only with the biology of the developmental stages of <i>R. arvalis</i> but also with the specifics of urban ecosystems. Five types of anomalies were identified in <i>R. arvalis</i> larvae at different stages of ontogenesis, which apparently may be initiated by mass infection of amphibians with metacercariae of the trematode <i>O. ranae</i>.</p>