The present study carried out to clarify the impact of heavy metals (Fe, Zn, Cu, Mn and Cd) pollution of Rosetta Branch on the antioxidant defence system activities and lipid peroxidation indicator MDA levels in O. niloticus tissues (liver and white muscles) collected from three stations from Rosetta Branch of River Nile in summer2014 and winter 2015. Rosetta Branch of River Nile exposed to high input of agricultural drainage water, sewage and industrial waste water which influence the living organisms especially fish. In the present study results revealed that the concentration of heavy metals (Fe, Zn, Cu, Mn and Cd) in water and fish samples increased in station II and III, especially in winter. In muscles of O. niloticus, the accumulation patterns of heavy metals were in the following order: Fe > Zn > Mn > Cu and Cd. The bioaccumulation factor (BAF) in winter was higher than summer. Antioxidant enzymes (SOD, CAT, GPx, GST and GR) activities and the indicator of lipid peroxidation MDA levels showed a significant increase in liver and white muscles of O. niloticus, in stations II and III, especially in winter. Moreover, the antioxidant enzymes activities and MDA levels were higher in liver than white muscles.