Abstract: The influences of cadmium, a well known environmental pollutant, on different biochemical parameters in fresh water fish, Oreochromis niloticus exposed to sublethal concentration of 9.3 ppm, 0.5 of 96 h LC50, for 1, 4 and 7 days were investigated. Significant increases in the levels of blood glucose and the activities of glutamic pyruvic acid transaminase, glutamic oxaloacetic acid transaminase and alkaline phosphatase were observed in the fish treated with cadmium during all experimental periods. The levels of blood triglycerides and total protein were statistically elevated at second and last periods. Insignificant alterations in the levels of blood cholesterol were noted. The observed hyperglycaemia induced by cadmium might be explained in part by increasing rate of glycogenolysis or gluconeogenesis. The observed hypertriglyceridaemia and the elevations of glutamic pyruvic acid transaminase, glutamic oxaloacetic acid transaminase and alkaline phosphatase may be due to liver dysfunction. The observed hyperproteinaemia in the fish, Oreochromis niloticus following cadmium administration is possibly attribute to disorder of protein metabolism. However, the significance of the toxic effects of sublethal concentration of cadmium on the various biochemical parameters studied is discussed.