One of the many biomarkers for determining the effects of pollutants on fish is changes in organ histomorphology. This study sought to determine the effect of graded acute concentrations (0.30, 0.40, 0.45 and 0.50 g/L) of Erythrophleum suaveolens on the histology of gills and liver of mixed sex of Clarias gariepinus juveniles. A total of 120 C. gariepinus juveniles were exposed to the acute concentrations of the plant extract. Paraffin wax method and haematoxylin-eosin staining techniques of tissue processing were adopted for the examination of the gills and liver. Dose-dependent histopathological changes were observed in the two organs (gills and liver), i.e. histopathological alterations increased with an increase in the concentration of the plant extract. Gills showed lamellae fusion, haemorrhage, severe necrosis and desquamation of secondary lamellae and severe necrosis of primary lamellae, while the liver indicated necrosis of hepatocytes, congestion and swelling of the intratubular spaces. Structural alterations were evident in the gills and liver of C. gairepinus juveniles exposed to the concentrations of aqueous crude leaf extract of E. suaveolens.