We investigate the role of NO2 in dimethyl ether (DME) ignition with a combustion shock tube. Ignition delay times are measured at 987-1517 K and 4 and 10 atm. Different equivalence ratios (0.5, 1.0, and 2.0) and NO2 and DME concentrations are explored. NO2 promotes DME ignition, and the promoting effect becomes more pronounced at high NO2 concentrations or low temperatures. NO2 addidon also augments the influence of the equivalence ratio on ignition delay times. Four detailed reaction mechanisms from the literature are examined against the measurements, and an updated kinetic model is proposed and validated in comparison to experiments. On the basis of the updated model, sensitivity analysis, reaction flux analysis, and rate of production analysis are conducted to provide details on the kinetic effect of NO2 on DME ignition.