In the present study, a comprehensive numerical model of a Proton Exchange Membrane Fuel Cell (PEMFC) is developed and validated. The governing equations of mass diffusion, momentum transfer, species transport, heat transfer, and electric charge conservation are solved simultaneously. The simulations are performed using ANSYS FLUENT 15.0 at an operating temperature of 60 °C and atmospheric pressure. Model predictions are validated against experimental polarization data at the same operating conditions, showing good agreement. A mesh and iteration sensitivity analysis indicates that a mesh size of 224,280 cells and 500 iterations are sufficient to achieve a convergence criterion of 10⁻⁶. Increasing the mesh density or iteration number beyond these values increases computational cost without improving accuracy. The numerical results include contours of molar concentrations of hydrogen, oxygen, and water, as well as temperature, enthalpy, and entropy distributions. The results provide detailed insight into transport phenomena and thermodynamic behavior inside the Proton Exchange Membrane (PEM) fuel cell.