Measurements of the autoignition delays of dimethyl ether (DME)-enriched n-pentane mixtures were conducted at the equivalence ratios of 0.5-2.0, pressure of 20 atm, and temperatures of 1100-1600 K using a shock tube, and new data were provided for dual-fuel engine design, kinetic model development, and computational simulation. A recently published pentane isomer model was validated and used for kinetic analysis. It is found that the autoignition delay of n-pentane becomes longer as the equivalence ratio (fuel/air) increases. However, for DME, the dependence upon the equivalence ratio is inverse to that of n-pentane. Autoignition delays of DME/n-pentane mixtures become shorter with the increased DME proportion, except for the phi = 0.5 conditions, where the autoignition delays of DME and n-pentane are identical.