An environmental study of zooplankton on the Shatt al-Arab River was carried out in two stations from July until November 2018. A total of 34 taxa of zooplankton were recorded in this study, belong to Cladocera, Copepoda and Rotifera. Some species have disappeared and others have emerged during the study period but varying numbers of dominant species found during the search such as Acarocalanus gibber, and recorded in the station 1 in July and station 2 for all months such as cyclopoid nauplii of Copepoda. Water temperature ranged between (19-35) °C station 1 and between (18- 32) °C at station 2, Salinity values fluctuated between (4.05 and 15.42 ‰), (6.47- 12.2 ‰) at stations 1, 2 respectively. pH values ranged was between (7.3 to 7.9) and (7.1 to 8.5) at stations 1 and 2 respectively. Copepoda density ranged between (0.12 to 88.23) ind. l-1 at station 1 and between (0.94 to 69.73) ind. l-1 at station 2. Density of Cladocera fluctuated between (0.06 and 1.45) ind. l-1. Maximum and minimum densities were at station 1. The population density of Rotifera ranged between (0.06 ind. l-1 to 20.44) ind. l-1 at second station.