A mathematical model of a catalytic fin, a flat plate coated with a catalyst, operating under steady-state conditions where air carrying a fuel flows parallel to the surface, is developed. The model equations are derived from the basic equations of change, and model predictions of fin and boundary layer temperature are compared with experimental data for the combustion of propane and carbon monoxide (CO) over the flat plate coated with platinum(Pt)/alumina catalyst. Good qualitative agreement is found between the results of the experiments and the model predictions, although the model generally predicts higher fin temperatures and ignition of reaction to occur at lower temperatures.