In the present study, the density and abundance of zooplankton and its infections with ecto and endo parasites in Iraqi marine and estuarine brackish water of NW Arabian Gulf were studied. Sixty taxa of zooplankton were identified in the present study,35 taxa were copepods, while 25 taxa were belonging to other zooplankton. Eight taxa of Copepoda were recorded for the first time in the study area. Many type of protozoan parasites heavily infects copeopods and other zooplankton in the study area as follow: Ellobiopsis chattoni, Ellobiopsis sp., Thalassomyces sp., Blastodinium sp., Zoothaminium...