The study was conducted at the Shatt Al-Arab River at Ktiban creek  in three stations during the period from October 2017 to September 2018. The first station was in the Shatt Al-Arab near Al- Hartha power Station, the second and third stations were in the Ktiban creek. Samples were collected once a monthly. A total of 5106 fish were collected from the study, period included 24 species belong to 12 families, and consisted of eight marine species and 16 freshwater species (nine native and seven exotic species). Physical and chemical characteristics were measured during sampling period. water temperature, dissolved oxygen, pH, light penetration, salinity, current flow, total dissolve solid (TDS), nitrate, nitrite and phosphates The range of parameters  in the Shatt Al-Arab were within their normal levels except salinity values and TDS (8.7 PSU and 8210 mg /l respectively). The values of the diversity index (H) were calculated in the study stations between 1.06 -1.87 and evenness index (j) ranged from 0.42 -0.83and richness index(D) between 1.00 -2.62.