Abstract: Central composite response surface design was used to investigate and optimize the reaction conditions for conversion of L. siceraria seed oil into biodiesel with calcium oxide supported on kaolin as catalyst, whose concentration was held constant. The results (biodiesel yield) were fitted into a full quadratic model. Methanol to oil molar ratio and reaction time followed by temperature were found to be variably effective on the yield. The optimum and most economical condition for transesterification of L. siceraria oil to biodiesel was when the temperature, reaction time and methanol to oil molar ratio are held at 70.5°C, 60 min and 6.83, respectively. The model obtained has good predictive power. The catalyst was observed to be more effective in catalyzing the transesterification than either neat CaO or neat kaolin. The oil produced from the conversion process was found to meet most of the standard specifications set EU and ASTM.