In the present investigation, Jatropha curcas oil blended with diesel was used as an alternative fuel for the compression ignition (C I) engine. The performance and combustion parameters of the engine using blends and Jatropha oil were evaluated in a single cylinder CI engine and compared with diesel. Significant improvement in engine performance was observed in blended fuels compared to Jatropha oil. The specific fuel consumption of the blended fuels was also reduced as compared to Jatropha oil due to decrease in viscosity of blends. Acceptable thermal efficiency of the engine was obtained with blends containing 20% volume of Jatropha oil as compared to diesel value. At maximum load, the thermal efficiency of diesel, 20% Jatropha oil and diesel blend was found 24.212% and 19.48%, respectively. Ignition delay was higher with Jatropha raw oil and Jatropha oil diesel blends as compared to diesel fuel. Peak pressure and rate of pressure rise were lower as compared to diesel and total combustion duration for raw Jatropha oil and Jatropha oil diesel blends were higher than that of diesel. The lowest smoke emission was found in the 20% Jatropha oil and diesel blend as compared to entire blends and Jatropha oil as compared to diesel fuel. For 20% Jatropha oil and diesel blend, smoke emission was found to be around 5%-20% higher than that of diesel fuel for all load conditions. From the performance and combustion analysis, it has been concluded that 20% of Jatropha oil could be substituted for diesel without any engine major modification.