This paper aims to present a numerical simulation study based on finite elements method of the thermo-electro-mechanical behavior for a thermoelectric module (TEM) under operating conditions. The main goal is to scrutinize and find explanations for module loss of performance and reliability. Both of the electricity and cooling generation and the thermo mechanical behavior are analyzed. Under a constant heat flux of energy density close to 25.9 kW/m², a maximum temperature and deformation of 219 °C and 11.7 μm are obtained for the tested module. The temperature difference increase between upper and lower surface of the module has positive effect on the released power. The heat transfer coefficient value of the cooling fluid used for the module lower surface is found characterizing the water. Moreover, in open circuit, the tension increases as the length of the leg increases. Finally, the cooling capacity (Peltier effect) and the coefficient of performance COP of multi-stages module are investigated. For single stage module, the COP was maximum for a current intensity close to 0.4 A and COP >0.8 between [0.35A, 0.45A] and the increase of the stages number resulted in a decrease of the COP.