ABSTRACT— With increasing environmental consciousness and the depletion of fossil petroleum fuels, biofuel is being promoted as a green alternative to diesel fuel. Biofuel lowers pollution emissions without having to make major changes to existing engines. Biodiesel is different in its chemical and physical properties based on the types of material or oils used in its preparation. In this research, biodiesel from Jatropha seeds is used as a fuel to run a four-stroke, single-cylinder diesel engine using various blend ratios (B20, B40, B60, B80, and B100) and different loads (no-load, 25% load, 50% load, 75% load, and full load). Performance parameters were evaluated such as brake specific fuel consumption (BSFC), brake thermal efficiency (ηth), volumetric efficiency (ηv), and exhaust gas temperature, while exhaust emissions include specific emissions of HC, CO, CO2, and NOx. Biodiesel blends (B20%) reduce brake thermal efficiency by 6% and volumetric efficiency by 3% while brake-specific fuel consumption increases by 15%. As the blend increases, the emission of NOx increases, for pure Jatropha biodiesel NOx increases by 30% compared to pure diesel. Moreover, for 100% blend, the emissions of CO2 decrease by 35% and CO decreases by 55% compared to diesel fuel. As biodiesel proportions in fuel blends increase, HC and smoke emissions decrease. Results show that biodiesel made from non-edible oils, such as Jatropha, might be a viable substitute for diesel fuel.