In this work is presented a multiscale model for a Proton Exchange Membrane Fuel Cell (PEMFC) composed by a kinetic model for the oxygen reduction reaction (ORR) studied with Density Functional Theory (DFT), and a macroscopic transport model for the diffusion layers and the membrane. Values of water partial pressure at the boundaries of the electrodes and global electro-osmotic drag coefficients are obtained for different humidity of reactive gases and current densities. These quantities are compared with: i) the model itself but assuming the kinetics described by Faraday Laws and ii) experimental data. It is found good consistency between the calculated values and the experimental data. Also, it was obtained better degree of prediction with respect to the kinetics described by only the Faraday laws, especially for low current densities and similar inlet humidity of reactive gases. Because of the results obtained, the multi-scale strategy applied was considered appropriated and a notorious improvement is obtained for the description of the kinetic and transport phenomenology involved in the operation of PEMFC’s.