In this study, effect of EN addition to diesel-ethanol blends as cetane improver were examined with regard to performance parameters such as brake torque, brake power, fuel consumption, brake specific fuel consumption and exhaust emissions such as NOx, CO, CO2 in a four-cylinder, water-cooled diesel engine. Firstly, an ethanol-diesel blend represented as E10 were prepared by mixing 10% of ethanol with 90% of diesel fuel as volume. Then other blends symbolized as E10EN2 (10% ethanol, 2% EN and 88% diesel), E10EN4 (10% ethanol, 4% EN and 86% diesel) and E10EN6 (10% ethanol, 6% EN and 84% diesel) were created by mixing ethanol-diesel-EN to get information about the behavior of EN. The results obtained for these blends at five different engine speed under full load condition were compared with E10 and 100% diesel fuel. It was found that EN addition raised the cetane number by 5%, 11%, 16% for E10EN2, E10EN4 and E10EN6 compared to E10 whereas EN caused a slight decrease in kinematic viscosity, lower heating value and a slight increase in density. It was also deduced that EN addition had a reducing  effect on  NOx, CO emissions and brake power while it had an increasing effect on CO2 emission and brake specific fuel consumption.