Abstract: The toxicity of the combination of xylene and diesel at 50:50 ratio on the African catfish (Clarias gariepinus) was investigated using static bioassays for 96 h. No statistical significance was observed from the othergroups and the control group. Physicochemical parameters after exposing C. gariepinus to xylene: diesel for 24 h was no significant difference (p>0.05) among the different concentration gradients and there was also an increase variation along concentration gradient observed after 96 h. The behavioral responses of the test fish were observed at 24-96 h of exposure. Normal behavioral responses were observed in the control. Fish exposed to 25-50 mg L^-1 showed normal behavior from 24-48 h but afterwards, the fish that were alert stopped swimming and remained static for a while in response to the sudden changes in the surrounding environment. Generally, fish exposed to higher concentrations such as 100-250 mL L^-1 of the test chemicals showed progressive hyperventilation and abnormal behavior such as gulping of air, an erratic swimming movement, very fast swimming, jumping and displaying a vigorous jerky movement suffocation and loss of reflex. A faster opercula and tail beat movement was also observed with Spiraling. The behavioral responses increased significantly (p<0.05) with increase in concentration per time as compared to the control group of fish. Noticeable behavioural difference was recorded for the different concentration. An eco-friendlier chemical known LC₅₀ that is within the acceptable level recommended by WHO in well simulation and cleaning for a sustainable biodiversity and healthy aquatic environment.