Transesterification is a very slow reaction due to limited solubility of alcohol in vegetable oils that strongly affect the reaction rate. Application of phase transfer catalyst (PTC) can be advantageous to improve the solubility of alcohol in oils and increase the rate of reaction. Use of cetyltrimethylammonium bromide (CTMAB) as a PTC on in-situ transesterification of J. curcas l. with alkaline methanol was investigated. Response surface methodology (RSM) was used to statistically evaluate and optimize the in situ transesterification method of biodiesel production. The effects of process variables were investigated using 2 5 factorial and central composite design (CCD) technique. Mathematical model was developed to predict the yield of fatty acid methyl esters (FAME). After optimizing the process variables using the model equation, FAME yield (88.25wt ) was predicted and compared with the experimental yield (89.3 ± 0.7wt ) obtained at optimal condition. There is a good agreement between the predicted value and the experimental result. © 2011 IEEE.