Combustion and emission characteristics of a direct-injection diesel engine fueled with diesel-diethyl adipate blends were investigated. The results show that the ignition delay and the amount of heat release in the main combustion duration increase. The diffusive combustion duration and total combustion duration decrease, while the amount of heat release in the diffusive combustion increases with the increase of the oxygen mass fraction in the blends. Both the maximum mean gas temperature and the duration of high gas temperature decrease with the oxygen mass fraction in the blends. For a specific engine load and engine speed, the center of the heat release curve moves close to the top-dead-center, and the brake specific fuel consumption (bsfc) increases with the increase of the fraction of diethyl adipate; however, the diesel equivalent bsfc decreases and the thermal efficiency increases with the increase of the oxygen mass fraction in the blends. For 100% engine load, the largest value of eta(et) is given in the range of engine speed from 1400 to 2000 rpm. The exhaust smoke concentration decreases and the exhaust NOx concentration gives a slight variation with the increase of the oxygen mass fraction in the blends. A flat NOx /smoke tradeoff curve is presented when operating on the diesel-diethyl adipate blends. The study shows that utilization of diesel-diethyl blends combining with postponing the fuel delivery advance angle can simultaneously decrease both smoke and NOx emissions.