Damietta Nile Branch is a continues resource for drinking water and aquatic life in Delta Governorates; however it's subjected to severe pollutants of domestic, sewage and agri­cultural pollutants. The present study was conducted to evaluate seasonal accumulation of some heavy metals (Cu, Fe, Mn and Zn) in water, sediment and edible organs of the cichlid fish, Oreochromis niloticus, inhabiting El-BagouriaCanal during the period from summer 2013to spring, 2014. on the bases of qualitative and quantitative analysis, total protein, total lipids, total carbohydrates, ASAT and ALAT activity in the target organs (liver, kidney, muscle and gonads) of this fish were determined. Results revealed that, concentrations of heavy metals in sediment were remarkably higher than in the surface water.  It was followed the order: Fe>Mn>Zn>Cu in the former and Fe>Mn>Cu>Zn in the latter. In the target organs, however, it was in the rank of Fe>Zn>Cu>Mn. Biochemical analysis indicated remarkable changes in the metabolic pathways and enzymatic activities. ANOVA (p> 0.05) showed highly significant differences between the different organs, seasons and metals. Also, there was a highly significant difference between biochemical parameters and a slight significant difference between the different seasons and organs. Constant monitoring of the water quality in the study area is needed to record any alteration in the water characteristics and reducing the impacts on the aquatic ecosystem.