Aquaculture is an extreme activity of valuable and fast sector and expansion worldwide, however there are concerns related to environmental sustainability. The current study was carried out to determine the relation between water quality and the occurrence of bacteria in cage farmed common carp (Cyprinus carpio) in Basrah Governorate southern Iraq. Water from floating cages were randomly sampled from seven sites along the Tigris River and Shatt al-Arab estuary from December 2012 to June 2013 and from October 2018 to May 2019. The water quality of each sample was measured, including the temperature, pH, iron, chloride, sulfide, ammonia, nitrite, phosphate, total suspended solids, conductivity, biological dissolved oxygen and chemical dissolved oxygen. A total of seventeen bacteial species were identified, including Aerococcus viridans, Streptococcus gordonii, Streptococcus thoraltansis, Staphylococcus lentus, Staphylococcus pseudintermedius, Staphylococcus lugdunensis, Kocuria kristinae, Lactococcus lactis spp < em>. lactis, Leuconostoc mesenteroides ssp. cremoris, Vibrio cholera, Sphingomonas paucimobils, Aeromonus hydrophila, Aeromonas veronii, Aeromonas sobria, Pasteurella testudinis, Elizabethkingia meningoseptica, and Pseudomonas aeruginosa. The results indicated that, despite the changes in the quality of the water, no association was detected between the alteration recorded and the occurrence of bacteria, whether in the water or sediment, during the period of study,