The purpose of this paper is to experimentally investigate the engine pollutant emissions and combustion characteristics of a diesel engine fueled with ethanol/diesel blended fuel. The experiments were performed using various proportions of ethanol/diesel blended fuels in a single-cylinder direct injection (DI) diesel engine. The engine performance parameters and emissions were measured and compared to those using the baseline diesel fuel. To gain insight into the combustion characteristics of ethanol/diesel blends, the engine combustion processes for blended fuels and diesel fuel were observed using an engine video system (AVL 513). The results show that the brake specific fuel consumption increased at overall engine operating conditions, but it is worth noting that the brake thermal efficiency increased by up to 1-2.3% with 10 and 15% ethanol/diesel blended fuels. It is found that engines fueled with ethanol/diesel blended fuels have higher emissions of total hydrocarbon (THC), and lower emissions of CO, NOx, and smoke. The results also indicate that the cetane number improver has a positive effect on CO and NOx emissions, but a negative effect on THC emission. Based on the engine combustion visualization and in-cylinder temperature field analysis by using the primary color method, it is found that the ignition delay increased, the total combustion duration and the luminosity of the flame decreased, and the peak combustion temperature decreased for ethanol/diesel blended fuels.