Heavy metals are generally referred to as those metals which possess a specific density or more than 5 g/cm³ and adversely affect the life cycle of living organisms. The study aimed to determine the lead accumulation in Clarias gariepinus and effects on the Catalase activity. The result revealed that the higher the concentration of lead introduced, the higher lead accumulated in the range of 0.020 +0.0021 mg/Kg – 0.616 + 0.0057 mg/Kg. The result showed the highest catalase activity of 6.000 mmol/min was found in 2.00 mg/kg concentration, followed by 3.00 mg/kg which had catalase activity of 4.900 mmol/min, 4.00 mg/kg which had catalase activity of 3.200 mmol/min while the least catalase activity was revealed on 1.00 mg/kg with a value of 0.494 mmol/min. Finally, the result revealed that highest catalase activity of 6.000 mmol/min was found in 0.593+0.0014 mg/Kg lead accumulation, followed by 0.538+0.0134 mg/Kg lead accumulation which produced a catalase activity of 4.900 mmol/min, 0.616 +0.0057 mg/Kg lead accumulation had catalase activity of 3.200 mmol/min while the least catalase activity was revealed on 0.252+0.0417 mg/Kg lead accumulation concentration with a value of 0.980 mmol/min. sub-lethal concentration of lead has effect on catalase activity of Clarias gariepinus fingerlings does not cause mortality. Prolonged exposure however can lead to undesirable effects like shorter life span.