The need to boost food productivity to meet the demands of the ever-increasing human population necessitates the frequent use of agrochemicals. Primextra Gold containing atrazine (329g/l) and S-metolachlor (400g/l) is commonly used in agriculture to control weeds, especially in rice paddies. Given that herbicides could harm non-target species like fish, this study examined the effects of Primextra Gold on the behaviour, haematology, blood biochemistry and kidney of Clarias gariepinus. Juvenile C. gariepinus mean weight (11.05±5.43g) and length (11.95±6.13cm) were exposed to lethal and sublethal concentrations of the herbicide. The toxicity assay showed that the median lethal concentration (LC₅₀) was 3.63µg/l. The fish exposed to sublethal concentrations exhibited signs of asphyxiation. The white blood cell (9.410.8×106), aspartate aminotransferase (40.01-60.01IU/l) and alanine aminotransferase (68.02-90.12IU/l) levels increased significantly (p<0.05) in the test group compared to the control. Contrarily, glucose (53.14-82.25mg/dl) and protein (3.129.38mg/dl) were lower in the herbicide exposed group compared to the control (p <0.05). Kidney histopathology revealed focal loss of the renal tissue, mild intra renal haemorrhage, moderate focal loss of renal tissue and severe focal loss of
renal tissue in the herbicide exposed fish. The findings of this study suggest that this herbicide is hazardous to aquatic life and has negative consequences for non-target species when used indiscriminately. It is recommended that the herbicide should be used with caution, especially near aquatic habitat to maintain good water quality and ensure sustenance of aquatic biodiversity.