Combustion and emission characteristics of a direct-injection diesel engine fueled with diesel-diglyme blends were investigated. The results show that the ignition delay and the amount of heat release in the premixed combustion phase decrease with the increase of the oxygen mass fraction in the blends. The diffusive combustion duration and the total combustion duration decrease, while the amount of heat release in the diffusive combustion phase increases with the increase of the oxygen mass fraction in the blends. The maximum mean gas temperature in the cylinder increases and the duration of the high gas temperature decreases with the increase of the oxygen mass fraction in the blends. The center of the heat-release curve moves close to the top dead center and the effective thermal efficiency increases with the increase of the oxygen mass fraction in the blends. Moreover, the smoke concentration decreases with the increase of the oxygen mass fraction in the blends. Under the high engine load, smoke decreases by 3.7% for a 1 wt % increase of the oxygen mass fraction in the blends. The NO, concentration shows a slight decrease or remains unchanged with the increase of the oxygen mass fraction in the blends.