In the current global situation, organizations are required to achieve decarbonization. To reach this goal in the transportation field, one possible solution could be the electrification of vehicles. Fuel cells represent an optimal solution to pursue this goal. This dissertation aims at developing a thermal model of a Proton Exchange Membrane Fuel Cell in a Simulink environment that will be later integrated into the hybrid powertrain of a heavy-duty vehicle. Thermal management is crucial for a fuel cell system, particularly in automotive applications. In fact, during load variations, temperature changes impact negatively the efficiency of the fuel cell to the extent that at high temperatures the functioning can be irreversibly compromised.