The toxicity of cypermethrin (a pesticide) on fingerlings of African catfish, Clarias gariepinus was investigate with emphasis on histopathological effects. The juvenile were exposed to 0, 1.0, 2.0, 3.0, 4.0 and 5.0ppb of cypermethrin under experimental condition. The growth, nutrient utilization and feed utilization parameters (Weight gain, Average Daily Weight Gain, Percentage Weight Gain , Specific Growth Rate , Feed Intake ,Feed Conversion Ratio and Protein Intake were not significantly different(P>0.05) at the different concentration. However, histopathological changes were observed on the gills and liver of the experimental fish. In the gills, filament cell proliferation, cellular infiltration, haemorrhage and gill damage were observed. In the liver, there was vacuolation of hepatocytes and necrosis. However, there was no observable histological change in the intestine at the various concentrations of exposure. Respiratory stress, erratic swimming and instant death of fish were observed in exposed fish, which varies with the concentration of the toxicant and it showed that mortality increased with increase in concentration. This study concluded that Cypermethrin is highly toxic to fish and therefore should be avoided in aquatic ecosystem.