The spray characteristics of a blended fuel containing conventional diesel fuel and unrefined biodiesel fuel were investigated. Experiments were performed to analyze the effects that blending ratio and injection pressure have on the spray behavior. The process of spray injection was analyzed through a laser diffraction particle analyzer (LDPA). In addition, spray atomization characteristics were studied using the Sauter mean diameter (SMD) as well as the droplet concentrations under various injection conditions. Fuel containing unrefined biodiesel fuel exhibited different spray patterns in comparison to conventional diesel fuel due to the fuel’s high viscosity and large surface tension. The results indicate that the increase of injection pressure causes the SMD to become smaller. In contrast, an increase in the mixing ratio causes the SMD to become larger.