Over alternative technologies, the use of thermoelectric modules often provides solutions to many difficult thermal management problems where a low to moderate amount of heat is to be handled by simply regulating input voltage. Mathematical modeling of thermal behaviors with working condition parameters is required for practical cooling/heating control design. The article presents a methodology not only to experimentally determine the parameters of the thermoelectric modules in a few steps of measurement, but also to propose input-output descriptive models, which are a readable representation of nonlinear input-output relations for practical cooling/heating control design under working conditions. In this study, three thermoelectric modules with capacities of 45, 60, and 91.2 W are investigated experimentally as concrete examples. Unknown parameters of those thermoelectric modules, including the Seebeck coefficient, the electrical resistance, and the thermal conductivity are determined for the input-output descriptive models based on measurements. To illustrate effectiveness of the proposed methodology, the input-output descriptive model of a 45-W thermoelectric module is used to describe the actual thermal behaviors of cooling/heating control in real-time implementation. The simulated results have very good agreement with the experimental results. © 2011, Society for Experimental Mechanics.