High temperature PEM fuel cells (HT-PEMFC) offer several advantages over low temperature PEM fuel cells (LT-PEMFC). Numerical modeling is a powerful tool to understand the thermo-chemical and physico-chemical processes that take place within the gas diffusion layer (GDL) and the catalyst layer (CL) during the cell operation. The objective of the current work is to develop an electrochemical model based on the elementary step charge transfer reactions that occur at the anode and cathode of the HT-PEMFC. Elementary step reaction for adsorption of CO is also incorporated to account for performance drop in presence of CO. The electrochemical model is incorporated into a quasi-two dimensional numerical transport model of the cell. The diffusive transport in the porous electrode (GDL + CL) is modeled using Dusty Gas Model (DGM). The resulting governing equations for the species transport are solved using the ODE solver CVode. The whole model is implemented in C++. © The Electrochemical Society.