Kautagi clay is a kaolin type deposit that is abundantly available in Niger State , Nigeria with potential for application in pollution control such as wastewater treatment. This study investigates the optimum conditions for modification of Kpautagi clay for application in refinery wastewater treatment. Sulphuric acid was used in the modification of the clay and the modification variables considered were acid concentration, activation time and temperature. To develop the optimum conditions for the modification variables, the sulphuric acid modified Kpautagi clay was applied in the treatment of refinery wastewater in column mode at a fixed flow rate and mass of adsorbent. The results obtained indicate that the optimum conditions for modification of Kpautagi clay for application in the treatment of petroleum refinery wastewater are: acid concentration of 4M ; activation time of 120min and activation temperature of 100°C. Therefore, the optimum conditions developed in this study for modification of Kpautagi clay could be applied for improved performance in the treatment of petroleum refinery wastewater.