The present study was conducted to determine the occurrence and vertical distribution of zooplankton community in the Al-Diwaniyah River during the period from the spring of 2015 to the winter of 2016. Three stations were chosen along the course of the river. The samples were collected from the middle-stream of the river at two depths 30cm and 60cm. Some physical and chemical properties of the water were studied such as: Air temperature, water temperature, pH, turbidity, light penetration, water flow and dissolved oxygen, also the study included some biological aspects which represented by a qualitative and quantitative study of zooplankton. The results showed that the total identified zooplankton taxa in the 30cm depth was 36, 45, 36 taxa at study stations respectively. While in the depth 60cm the study identified at first station was 50, 59, 34 taxa at study stations respectively. The dominance groups were Rotifera, Copepoda followed by Cladocera. A total number of zooplankton varied in depth 30cm and 60cm from 633 to 3367Ind./m3 and 2033 to 6933Ind./m3, respectively. Also the current study recorded two peaks of zooplankton community bloom, the first once in spring and the other in autumn. Finally it was concluded from the current study that the properties of water specially water flow velocity effects on the occurrence and vertical distribution of zooplankton, which are depending on sources and distribution of food, also it was founded that the number of the taxa and the total density in the depth 60cm was higher than its in the depth 30cm. published by the Journal of Biodiversity and Environmental Sciences | JBES