The effect of varying concentrations (0, 0.25, 0.05 and 1.0% v/v) of water soluble fraction (WSF) of crude oil on the growth performance and biochemical changes in the serum and liver of 144 Clarias gariepinus Juveniles stocked into 12 glass aquaria at the rate of 12 fish per tank in triplicate for 90 days was assessed. The growth performance indices of the fish juvenile over the 90 days of toxic exposure revealed that the mean weight gained, specific growth rate, and total feed intake of the fish specimen decreases with increase concentration of the WSF of crude oil. However, 10% and 20% mortality were recorded in the fish exposed to 0.5% and 1.0% WSF of crude oil respectively. The activity of ALT and AST in the serum of the fish were significantly higher (p<0.05) with the increased concentration of WSF of crude oil while the ALT and AST activity of the liver of the fish juveniles irrespective of the added concentration of WSF of crude oil showed no significant differences (p>0.05). The study concluded that WSF of crude oil had adverse effects on the growth performance, blood serum and liver activities in C. gariepinus juveniles.