Understanding the process of penetration and distribution of the invasive species Sinanodonta woodiana is important for predicting associated changes in biodiversity and the structure of freshwater communities. The biomass, density, age and sex structure of mollusk populations were analyzed. An increase in the size of Chinese pond mussels was noted after the introduction: the shell length of individuals from a pond (Romanivka village, 2017) was 24,2% more than of mollusks from the Velyka Repida river (Matroska village, 2004), and in 2019 it increased by another 14,7% (by 42,5% compared to the shell length of the mollusks from the Velyka Repida river). The body weight of S. woodiana from the river was 125,3 g, while in the pond there was a 2,13-fold increase in body weight in 2017, with a further increase in this indicator by another 23,6% in 2019 and another 37,7% in 2020. The relative number of S. woodiana and native species Unio pictorum and Anodonta anatina in 2017 was 26,3%, 47,4% and 26,3%, in 2020 – 64,0%, 16,0% and 20,0% respectively. Ciliates of the genus Conchophthirus and Trichodina, Aspidogaster conchicola, Helobdella stagnalis, larvae of Chironomus sp. are in a symbiotic relationship with S. woodiana. The most common Conchophthirus sp. – in 21,6% of individuals. Further spread of S. woodiana to the cold regions of Ukraine and the formation of new populations in the already developed regions should be expected.