In present work, some biochemical characteristics of the catfish, Clarias gariepinus were studied under the effect of different sublethal doses of 4-nonylphenol (0, 0.05, 0.08 and 0.1 mgl-1). Liver enzymes ALT and AST increased insignificantly at P0.05 whereas the ALP decreased insignificantly. The activities of G6PDH showed significant increase with the increased sublethel doses of 4-nonylphenol while the activities of LDH decreased insignificantly with increase of such doses. The concentrations of serum glucose and total cholesterol significantly increased after exposure to 4-nonylphenol, although Hyperglycemia is evident. The kidney function parameters such as total serum protein and uric acid increased insignificantly after exposure to 4-nonylphenol in comparison with the control fish whereas creatinine exhibited significant increase (P0.05). Some serum ions decreased significantly (HCO3 - and Na+) or insignificantly (Cu+2, Cl- and Ca+2) and others increased significantly (Fe+2) or insignificantly (K+) under 4-nonylphenol stress on C. gariepinus. Increased serum anion gap was associated with increased hyperglycemia and insignificant hypocalcemia. Such increased gap referred to nonylphenolinduced metabolic acidosis. The adverse impact of the sublethal doses of 4-nonylphenol on the molecular structure of the protein was evident by electrophoresis. In conclusion, in addition to its tissue-specific estrogenic effects, 4-nonylphenol has non-estrogenic adverse effects on liver and kidney functions through activation of other metabolism-related genes distinct from estrogenresponsive genes.