Sublethal toxicity of cyanide to freshwater fish, Cirrhinus mrigala was evaluated to determine its effect on the activities of some antioxidative enzymes. Changes in succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6-PDH) were observed in tissues of the tested animal. Cyanide significantly decreased the activity of SDH, and G6-PDH in the liver, gill and brain tissues of the fish. The elevation of LDH indicated metabolic disorders and a clear response against energy depletion. Changes in the dehydrogenase activity in cyanide treated fish tissues may be due to fluctuations in oxidative metabolism. It is concluded that the cyanide intoxication exerted a profound impact on the enzymatic activity of the fish, as observed in the hitherto study.