The aim of this work is to investigate the effect of the bioethanol addition on the spray behavior and atomization characteristics of biodiesel fuel. Spray behavior characteristics were studied by analyzing the spray Lip penetration. spray centroid, and spray cone angle. In addition, the spray Lip penetrations estimated by theoretical and empirical equations were compared with the experimental results. Droplet size and axial velocity were investigated for analyzing the fuel atomization characteristics. Bioethanol fuel was blended with biodiesel fuel derived from soybean oil in a volumetric ratio from 10 to 30% in 10% intervals. It was revealed that the blending ratio of bioethanol fuel had little effect on the spray tip penetration. The spray cone angle of blended fuels was increased by adding the bioethanol fuel. When the ambient gas temperature increased, the spray tip penetration of an undiluted biodiesel fuel increased due to the decrease in ambient gas density. However, the spray tip penetration of bioethanol-biodiesel blended fuels decreased due to fuel evaporation caused by high ambient gas temperature. This is due to the fact that bioethanol has high volatility and a low boiling. point (about 783 degrees C). In the case of the atomization characteristics, when bioethanol was added to biodiesel. the droplet size of bioethanol blended fuels decreased and the ratio of smaller size droplets increased. Based oil these results, it is possible to maintain the overall spray characteristics of biodiesel and simultaneously, improve atomization performance when bioethanol is added to biodiesel.