Wood pyrolysis oil (WPO) is considered as an alternative fuel for compression ignition engines. But, due to its poor combustion characteristics, it requires significant modification in the fuel to solve problems like miscibility, presence of water content etc, when it is used as an alternative fuel in compression ignition engines. In this study, an attempt is made to use wood pyrolysis oil-bio diesel emulsions in a diesel engine. Three emulsions of WPO and Jatropha methyl ester (JME) were obtained with the help of a surfactant, and used as fuels in a single cylinder, four stroke, air cooled, direct injection diesel engine. The emulsions were designated as WPO5, WPO10 and WPO15 where the numeric value indicates the percentage of the WPO in the emulsion. The performance and emission characteristics of the engine were obtained, analysed, and compared with those of diesel fuel and presented in this paper. The emulsions made with WPO15 show an improved performance and lower emissions than WPO5 and WPO10. Compared to diesel at full load, 11.3% higher brake thermal efficiency was achieved with WPO15. HC emissions were found to be lower by about 50% for WPO15 than for diesel fuel at full load. It is observed that about 3% lower NO emissions were obtained with WPO15 at full load in comparison with diesel. The smoke opacity of WPO5 is lower by 22.7% at full load than that of diesel.