•Finite Element simulation to determine the thermal conductivity of membranes.•Thermal conductivity of 8 commercial polymeric membranes was estimated.•The method only requires knowledge of membrane thickness and density.•A simple experimental setup modelled in Comsol provides the temperature gradient fitted to the experimental one under steady conditions. The aim of this study is to calculate the through-plane thermal conductivity of commercial polymeric ion-exchange membranes. Different membranes were considered to study the influence of membrane properties on the thermal conductivity values. In particular we focused on reinforcement, ion exchange capacity and membrane density and thickness. For this purpose, we use a simple experimental setup and a numerical simulation to estimate the thermal conductivity from the experimental temperature profiles. Once the system is calibrated, the model includes as the only unknown parameter the membrane thermal conductivity. To validate the method, the thermal conductivity of the well-known Nafion membranes has been determined, a very good agreement was achieved in context from reliable literature values. The study also provides the thermal conductivity of other polymeric ion-exchange membranes with great potential in diverse applications under non-isothermal conditions. The calculated thermal conductivity for the different ion-exchange membranes is in the range from 0.04 Wm−1K−1 to 0.42 Wm−1K−1. The results show that the reinforcement leads to lower values of thermal conductivity whereas a higher density or heterogenous structure leads to higher thermal conductivity values. The approach presented here, combining experimental and simulation techniques, may provide a basis for confirming the effect of the polymeric ion-exchange membrane properties on the thermal conductivity and may shed light on the best choice for the electrolyte of membrane-based applications performance under non-isothermal conditions.