This study investigated the effects of the Zubaydiyah Power Plant (ZPP) on the biodiversity and the quantitative and qualitative composition of the rotifer community. Five sites along the Tigris River were chosen for sampling: Site 1, located upstream of the ZPP effluents; Site 2, near the ZPP; and Sites 3, 4, and 5, located downstream of the ZPP. Samples were monthly collected from January to December 2021. A total of 71 taxonomic units of rotifers were identified. The density of rotifers ranged from 31,843.3 to 755 individuals per cubic meter. The lowest number of species was recorded at Site 2.The relative abundance data indicated that eight species were the most abundant. A clear decrease in biodiversity, as measured by the Shannon-Wiener index, species evenness, species richness, and Jaccard's presence-absence index, was observed near the ZPP effluent site. The number of constant taxonomic units at Site 1 decreased from 26 to 12 near the ZPP effluents. However, as the influence of the ZPP effluents diminished, these taxonomic units gradually reappeared: 14 constant taxonomic units at Site 3, 18 at Site 4, and 27 at Site 5. The results demonstrate a clear negative impact of ZPP effluents on the diversity of the rotifer community.