This work considers the development of ammonia (NH3) by selective catalytic oxidation (SCO) over a honeycomb Pt-Pd-Rh ternary composite cordierite catalyst in a tubular fixed-bed flow quartz reactor (TFBR) at temperatures between 423 and 623 K. A honeycomb Pt-Pd-Rh ternary composite cordierite catalyst was prepared by incipient wetness impregnation with aqueous solutions of H2PtCl6, Pd(NO3)3 and Rh(NO3)3 that were coated on cordierite cellular ceramic materials. The catalysts were characterized using OM, TGA-DTA, SEM/EDX and TEM. Based on the experimental results show that around 99.5% NH3 removal was achieved during catalytic oxidation over the honeycomb Pt-Pd-Rh ternary composite cordierite catalyst at 623 K with an oxygen content of 4%. N2 was the main product in the NH3-SCO process over the honeycomb Pt-Pd-Rh ternary composite cordierite catalyst. Moreover, the present study also shows that contaminants crystal aggregation phases and washcoat loss may be responsible for the deactivation of the catalysts. These results also verify that the high initial concentration of the influent NH3 decreases the efficiency of removal of ammonia.