Transesterification of Sesamum indicum L. oil was carried with methanol in the presence of sodium methoxide and the parameters affecting the reaction; vegetable oil/methanol molar ratio, catalyst concentration, reaction temperature and time were fully optimized by employing Central Composite Design method (CCD). A quadratic polynomial was developed to predict the response as a function of independent variables and their interactions and only the significant factors affecting the yield were fitted to a second-order response surface reduced 2FI model. At the optimum condition of 1:6 oil/methanol molar ratio, catalyst concentration of 0.75% and reaction time of 30 min, biodiesel yield of 87.80% was achieved. The selected fuel properties were within the range set by ASTM and EN bodies.