Dimethyl ether (DME) and rapeseed oil are two kinds of promising alternative fuels for compression-ignition (CI) engines. Performance and emissions of a CI engine fueled with different proportions of DME/rapeseed oil blends are investigated in this paper. The results prove that an engine can run well with DME/rapeseed oil blends under all operating conditions. With an increase of the rapeseed oil concentration in blends, the power and torque of an engine can be improved. However, NOx emission becomes worse, simultaneously. Smokeless combustion can be realized with less than about a 6% rapeseed oil mass fraction in the blend. Above more than about a 6% rapeseed oil concentration, smoke emission occurs and becomes more and more severe with an increase of the rapeseed oil mass fraction. An increase in the rapeseed oil mass fraction will also result in an increase of the ignition delay, the fraction of fuel burned in the premixed combustion phase, and the maximum cylinder pressure.