The depletion of oil resources as well as the stringent environmental regulations has led to the development of alternate energy sources. In this work the combustion, performance and emission characteristics of a single cylinder diesel engine when fuelled with blends of jatropha and diesel oil are evaluated. Experiments were conducted with different blends of jatropha oil and diesel at various loads. The peak pressures of all the blends at full load are slightly lower than the base diesel. There is an increase in the ignition delay with biodiesel because of its high viscosity and density. The results show that the brake thermal efficiency of diesel is higher at all loads followed by blends of jatropha oil and diesel. The maximum brake thermal efficiency and minimum specific fuel consumption were found for blends up to B20. The specific fuel consumption, exhaust gas temperature, smoke opacity and NOx were comparatively higher. However there is an appreciable decrease in HC and CO2 emissions while the decrease in CO emission is marginal. It was observed that the combustion characteristics of the blends of esterified jatropha oil with diesel followed closely with that of the base line diesel.