Direct methanol fuel cells (DMFCs) are becoming a choice of a power source in the field of power electronics, and portable devices because of their high energy density. The benefits of using a fuel cell toward the environment will be enhanced if the fuel used for its application comes from renewable sources such as ethanol. A method of modeling of the performance of DMFC was developed and validated with the experimental data obtained from a passive DMFC operated under varying methanol and ethanol concentrations. Impedance spectroscopy was employed to measure ohmic, activation and mass transport losses for all concentrations. Improved performance of the cell was observed when the concentrations of the solutions were closer to stoichiometric values. The model predicted results were compared to the corresponding experimental values and found satisfactory.