In order to meet the growing global energy requirement, exhaustive research is carried to develop and use variety of renewable fuels. Main objective of the present study is to compare the performance, emissions and combustion characteristics of biodiesel derived from non-edible Karanja oil in an unmodified diesel engine and to compare the results with baseline results of diesel fuel. Important physicochemical properties of Karanja oil after transesterification were experimentally evaluated and found within acceptable limits of relevant standards. The performance parameters evaluated in the present study includes brake thermal efficiency of Karanja biodiesel with different compositions at 5%, 10%, 20%, 30% and 100% with mineral Diesel. BTE was about 3-5% lower with Karanja biodiesel and its blends with respect to diesel. Also, emissions parameters such as carbon monoxide, carbon dioxide, UBHC (unburned hydrocarbon), oxides of nitrogen and smoke opacity for different test fuels were also measured. UBHC, CO, CO2 and smoke were lower with Karanja biodiesel fuel. However, NOx emissions of Karanja biodiesel and its blend were higher than Diesel. The combustion analysis was done using peak cylinder pressure and heat release rate with respect to crank angle. The peak cylinder pressure and heat release rate was lower for Karanja biodiesel. The results from the experiments suggest that biodiesel from non-edible oil like Karanja and its blends with diesel could be a potential fuel for diesel engine and play a vital role in the near future especially for small and medium energy production. (C) 2013 Elsevier Ltd. All rights reserved.