Biodiesel was prepared by transesterification of sesame seed oil with methanol in the presence of NaOH as catalyst. The optimization of this base catalyzed at 1:7, 1:8, 1:9, and 1:10 molar ratio (oil:methanol) yield maximum biodiesel 86, 88, 90, and 92%, respectively at 60 degrees C. The fuel properties of sesame biodiesel (100%) such as specific gravity @ 60/60 degrees F was 0.887, flash point 110 degrees C, pour point -18 degrees C, kinematic viscosity @ 40 degrees C 5.77, cetane number 53, and sulfur contents 0.0083. All these fuel properties meet the specification of ASTM. Engine fueling with sesame biodiesel and its blends (B20%, B10%, and B5%) in terms of fuel consumption, efficiency, and power outputs appeared to have equal performance compared to mineral diesel. There is no obvious change in engine power output even at 100% biodiesel. Furthermore, it was noted that the environmental performance of sesame biodiesel was superior to that of mineral diesel.