Paraquat herbicide, commonly used to control weeds in farms, could reach the aquatic environment and imperil non-target organisms through run-offs. This study was conducted to assess the impact of paraquat on African catfish Clarias gariepinus. Juvenile C. gariepinus weighing 19.06±7.43g, acclimatised for two weeks under laboratory conditions, were randomly divided into four groups of ten fish each and exposed to 0.00 (control), 794.33, 882.59 and 992.91µg/l of paraquat, labelled A, B, C and D, respectively. The experiment was performed in triplicate for 96 hours. Thereafter, two fish from each tank were removed, and blood was collected for haematological and biochemical analyses, while the kidneys were excised for histopathological examination. The results showed that red blood cells and packed cell volume decreased while the white blood cells increased significantly (p<0.05) compared to the control. The activities of aspartate aminotransferase and alkaline phosphatase significantly increased (p<0.05) while glucose and protein decreased significantly (p<0.05). Histopathological examination revealed concentration-dependent damage to the kidney of the paraquat-exposed groups. This study shows that paraquat is toxic to juvenile fish, therefore, caution should be taken in its application. Policies should be enacted and enforced to protect the environment and non-target species.