In this study, effects of emulsified fuels on the performance and emissions of a diesel engine were investigated experimentally. Effective power, specific fuel consumption and thermal efficiency as well as emissions of carbon monoxide, hydrocarbon, nitrogen oxide and carbon were considered as parameters for the investigation. Two emulsified fuels, namely B20W10 and B20W15, containing 10 and 15% water by volume, respectively, were prepared by using diesel fuel-biodiesel blend (B20). The emulsified fuels were tested in a naturally aspirated, direct injection diesel engine at partial load conditions. The test results obtained from the emulsified fuels were compared with those of neat diesel fuel and B20. It was found that the emulsified fuels yield higher specific fuel consumptions, while they cause only slight changes in thermal efficiency. The emulsified fuels are very capable of reducing NOx emission at all engine loads. On the other hand, the use of emulsified fuels brings about significant increase in CO and HC emissions at low engine loads, while they cause moderate CO and HC emissions at high engine loads.