The main goal of this research was to determine the ultrastructural characteristics of Paradilepis scolecina (Rudolphi, 1819) metacestode, which was first recorded in the territory of Azerbaijan in common carp (Cyprinus carpio L., 1758), and the pathological changes occurring in the ultrastructure of the parasite due to the effect of ZnO nanoparticles on the helminth. For this, light, electron microscopic methods and statistical analyses were used. Nanoparticles (ZnO) at 10 mg were used in vivo against parasites localized in the body cavity of common carp. The helminths collected from both control and experimental groups were studied by preparing araldite-epon blocks and taking semi- and ultrathin sections. Parasite and its capsule ultrastructure of were determined and main taxonomic features compared with the data of other researchers. It was found that due to the effect of nanoparticles (ZnO), numerous destructive changes occur in the fat tissue of intestinal mesentery where the parasite is localized, in all three layers (serous, fibrillar and hyalin layers) of the capsule of helminth, and in different layers of the parasite's body wall (tegument). It was determined that at higher magnifications (>100 000) on Transmission Electron Microscope (TEM) under experimental conditions ZnO nanoparticles used are bioaccumulated in the wall of the capsule and in the body of the parasite and their size is 10-15 nm. The zinc oxide nanoparticles used have antiparasitic properties and in the future it can be used for different fish helminthiasis.