This work aimed at evaluating the behavioral, biochemical and hematological effects of pharmaceutical effluent in laboratory population of Clarias gariepinus using a static renewal bioassay system. Fish specimens were collected and exposed to five (0.04, 0.06, 0.08, 0.10 and 0.12 mgL -1) sublethal concentrations of the effluent including a control experiment. Different dose dependent behavioral responses such as erratic swimming, gasp for breath, restlessness, and constant upward movement were observed in exposed fish. There was a steady decrease in the value of red blood cell (RBC), hemoglobin (Hb) and packed cell volume (PCV) as concentrations increase compared to the control stock. White blood cell count was found to be significantly (p<0.05) higher as the concentration of the test medium increases. Irregular level of lymphocytes and granulocytes across all concentrations was observed and levels of lymphocytes and granulocytes were significantly (p<0.05) increased in all effluent-treated fish samples during the exposure period. Different levels of total protein, glucose, cholesterol, etc., were obtained in the control and effluent-treated fish samples (p<0.05). The levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase (serum enzymes) and lactate dehydrogenase were significantly (p<0.05) higher in the exposed C. gariepinus. The hematological and biochemical alterations in the effluent treated C. gariepinus, which were strongly indicative of cellular damages. This might be attributed to toxic effects of the phamarceutical effluent. Consequently, direct discharged of untreated or partially treated pharmaceutical effluent should be discouraged as this calls for public health concern.