The efficiency of a Thermoelectric Module (TEM) is not only influenced by the material properties, but also by the heat losses due to the internal and contact thermal resistances. In the literature, the material properties are mostly discussed, mainly to increase the well-known thermoelectric figure of merit ZT. Nevertheless, when a TEM is considered, the separate characterization of the materials of the p and n elements is not enough to have a suitable TEM electrical model and evaluate more precisely its efficiency. Only a few recent papers deal with thermal resistances and their influence on the TEM efficiency; mostly, the minimization of these resistances is recommended, without giving a way to determine their values. The aim of the present paper is to identify the internal and contact thermal resistances of a TEM by electrical characterization. Depending on the applications, the TEM can be used either under constant temperature gradient or constant heat flow conditions. The proposed identification approach is based on the theoretical electrical modeling of the TEM, in both conditions. It is simple to implement, because it is based only on open circuit test conditions. A single electrical measurement under both conditions (constant-temperature and constant-heat) is needed. Based on the theoretical electrical models, one can identify the internal and thermal resistances.