The development of a mathematical model is presented, which simulates the performance of a non-isothermal packed-bed membrane reactor. The model takes into account the various heat exchanges that take place inside the reactor. A set of partial-differential conservation equations, coupled with the appropriate boundary and internal conditions describing the physical problem considered is solved, using finite-volume techniques. In this study, the developed mathematical model is applied to investigate the endothermic dehydrogenation of cyclohexane in a packed-bed membrane reactor, where a permselective porous glass membrane is embodied. It is shown that the assumption of isothermal conditions, or even the omission of certain thermal phenomena that take place inside the reactor, lead to a significant overestimation of the predicted temperature field and of the membrane reactor conversion.