Carbon-supported platinum and iridium catalysts were prepared for catalytic wet air oxidation (CWAO) applications. These catalysts were tested in the CWAO of butyric acid aqueous solutions at 200 °C and 6.9 bar of oxygen partial pressure, and significant conversions above 70% were obtained depending on the catalyst used. The long-term deactivation resistance of the Pt/C catalyst is higher than that of the Ir/C catalyst. The deactivation observed with the Ir/C catalyst was attributed to the overoxidation of the surface of iridium by molecular oxygen. A deactivation study of the catalysts was conducted using N2 adsorption, thermogravimetric analysis, temperature-programmed reduction, and X-ray photoelectron spectroscopy. A kinetic model describing the observed deactivation phenomena in the Ir/C catalyst is proposed and tested using the experimental data obtained in the CWAO of the systems studied.