Experimental investigations were carried out to study the effect of the addition of an ignition improver with a bioethanol diesel emulsion, on the performance and emission behavior of a single-cylinder, 4-stroke, air-cooled, direct-injection (DI) diesel engine, with a rated power of 4.4 kW at a constant speed of 1500 rpm. Bioethanol was produced from the madhuca indica flower, which is proposed as a new feed stock. 15% bioethanol was emulsified with 84% diesel on a volume basis with the help of a surfactant of 1% to get the emulsion named as BDE15. The ignition improver used in the experimentation was diethyl ether (DEE) whose cetane number is greater than 125. 1% and 2% of DEE was added to the bioethanol diesel emulsion named as BDE+DEE1% and BDE+DEE2% respectively. The performance and emission results of the engine fueled with BDE15, with BDE+DEE1% and BDE+DEE2% were compared with those of diesel operation, and are presented in the paper. The results showed that BDE15 with or without the ignition improver, showed a lower thermal efficiency and higher brake specific energy consumption than that of diesel operation. The oxides of nitrogen (NO) emission was found to be lower for BDE15, but smoke was found to be higher compared to that of diesel and BDE15 with ignition improver throughout the engine operation. With the addition of the ignition improver, the NO emission decreased at full load compared to that of diesel. There is a reduction in smoke emission with addition of ignition improver compared to that of BDE15 and diesel operation in the entire engine operation.