Thirty-eight Mallards were collected on the territory of Ukrainian Polissia to study the fauna of their gastro-intestinal helminths. Materials were collected in 1998–2000, 2014 and 2016 on the territory of Volyn and Chernihiv Regions. In total, 33 species of helminths were found. The prevalence of cestode infection was 78.9 %. We found 18 cestode species: Aploparaksis furcigera, Cloacotaenia megalops, Dicranotaenia coronula, Diorchis acuminatus, D. stefanskii, Fimbriaria fasciolaris, F. teresae, Microsomacanthus compressa, M. spiralibursata, M. paracompressa, M. paramicrosoma, M. parvula, M. hopkinsi, Platyscolex ciliata, Retinometra venusta, Sobolevicanthus aculeostyleticus, S. gracilis, S. stolli. The prevalence of trematode infection was 73.7 %. There were 10 trematode species: Bilharziella polonica, Apatemon gracilis, Echinoparyphium aconitum, E. cinctum, Echinostoma revolutum group, Hypoderaeum conoideum, Notocotylus attenuatus, Parastrigea robusta, Prosthogonimus ovatus, P. cuneatus.The prevalence of nematode infection was 7.9 %. There were four nematode species: Capillaria anatis, Capillariidae gen. sp., Eucoleus contorta, Tetrameres fissispina. The prevalence of an acanthocephalan Filicollis anatis was 18.4 %. The most common species of helminths were A. furcigera, B. polonica, A. gracilis, Echinostoma revolutum group, F. fasciolaris, H. conoideum. The helminth faunas of Mallards from the territory of Ukrainian Polissia and from the Black Sea Region of Ukraine were compared. The results of comparison demonstrated a high level of their qualitative similarity.