Biodiesel is an alternative to petro-diesel which is a fatty acid methyl ester of animal fats and vegetable oils. A technique to produce biodiesel from occidentalis oil having high free fatty acids (17% FFA) has been developed. The high FFA level of occidentalis oils was reduced to less than 1% by a two-step pretreatment process. The main objectives of the present work are to reduce the higher viscosity of occidentalis oil using esterification followed by transesterification and to assess the performance. Each step was carried out with 0.30 -0.35 v/v methanol-to-oil ratio and with the presence of 1% v/v H(2)SO(4)as an acid catalyst during 1 h reaction. The mixture was allowed to settle for an hour and the methanol-water mixture was separated from the top of the mixture. The second step is transesterification of the bottom layer using 0.25% v/v methanol and 0.7% w/v KOH as an alkaline catalyst to produce biodiesel. The fuel properties of Senna occidentalis biodiesel were found to be comparable to that of American and European standard petro-diesel.