Presently, many methods are adopted to reduce the junction-to-case thermal resistance of insulated-gate bipolar transistor (IGBT) modules in order to increase their power density. One of these approaches is to enhance the heat spreading capability of the base plate (heat spreader) of an IGBT module using a vapor chamber (VC). In this paper, both experimental measurement and thermal modeling are conducted on a VC-based IGBT module and two copper-plate-based IGBT modules. The experimental data show that of the VC-based IGBT module decreases substantially with the increase in the heat load of the IGBT. of the VC-based IGBT module is of that of the 3 mm copper-plate-based IGBT module after it saturates at a heat load level of . The transient time of the VC-based IGBT module is also shorter than the copper-plate-based IGBT modules since the VC has higher heat spreading capability. The quicker responses of the VC-based IGBT module to reach its saturated temperature during the start-up can avoid a possible power surge. In the thermal modeling, the vapor is substituted as a solid conductor with extremely high thermal conductivity. Hence, the two-phase flow thermal modeling of the VC is simplified as a one-phase thermal conductive modeling. A thermal circuit model is also built for the VC-based IGBT module. Both the thermal modeling and thermal circuit results match well with the experimental data.