A compact analytical model is proposed for predicting thermal joint resistance of rough polymer-metal interfaces in a vacuum. The model assumes plastic deformation at microcontacts and joint temperatures less than the polymer’s glassy temperature. The joint resistance includes two components: (i) bulk resistance of the polymer, and (ii) microcontacts resistance, i.e., constriction∕spreading resistance of the microcontacts at the interface. Performing a deformation analysis, it is shown that the deformation mode of surface asperities is plastic for most polymers studied. It is observed that the thermophysical properties of the polymer control the thermal joint resistance and the metallic surface properties have a second order effect on the thermal joint resistance. A new nondimensional parameter, the ratio of microcontacts over bulk thermal resistances, is proposed as a criterion to specify the relative importance of the microcontacts thermal resistance. The present model is compared with more than 140 experimental data points collected for a selected number of polymers. The averaged rms relative difference between the model and data is approximately 12.7%.