Rosetta branch is a source of fresh water for domestic, agriculture, industry, fisheries and recreation purposes for some western Delta governorates in Egypt. Unfortunately this branch is impacted by increasing concentrations of ammonia resulted from the agricultural drains located along its sides and by the industrial effluents of industrial activities and fish farming cages. This study aims at monitoring ammonia, dissolved oxygen nitrite and nitrate concentration along the Rosetta branch. Samples were taken at an interval of 5 Km of the branch. Ammonia concentrations measured by a colorimetric Nessler method. Recorded ammonia ranged from 0.16 to 7.87 mg/l. Level of ammonia in Rosetta branch is very high after mixing with Rahawy drain, as it reached 6.77 mg/l and decreased gradually along the Rosetta branch to the lowest level of 1.67 mg/l at Kafr Yaqob village due to dilution along the branch and increased again, due to presence of fish cages along Gharbiya, Kafrelsheikh and Behaira governorate.