The establishment of self-sustaining cool premixed flames by the addition of ozone in dimethyl ether/oxygen mixtures has been explored numerically through one-dimensional free propagating flames and then experimentally confirmed in the counterflow configuration for the first time. In the calculation of freely propagating flames with ozone sensitization, three different flame regimes were found-conventional high temperature flames, low temperature cool flames, and transitional flames. The flame structures of cool flames and transitional flames are much different than those of conventional high temperature flames. It was also found that these cool flames significantly extend the lean flammability limit. For the counterflow configuration, the existence of stable cool flames was demonstrated over a broad temperature range. The results showed that increases in the initial inert temperature expand the flammable region of stable cool flames and can dramatically modify the cool flame ignition limits. The existence of stable cool flames was further confirmed by experiments in which the extinction and stability limits of cool premixed flames were measured for the first time. This study has not only provided insights into ozone-sensitized cool flames but has also established a new platform to study and understand cool flame dynamics, structure, and chemistry.