The oxide supports play a crucial role in anchoring and promoting the active metal species by geometric confinement and chemical interaction. The design and synthesis of the well-defined oxide support with specific morphology such as size, shape, and exposed facets have attracted extensive research efforts, which directly reflects on their catalytic performance. In this study, using an Au/CeO₂-nanorod model catalyst, we demonstrate an edge effect on the Au/CeO₂ interfacial structure, which shows a prominent effect on the structure–performance relationship in the CO oxidation reaction. This specific “edge-interface” structure features an “edge-on” Au nanoparticles position on rod-shaped CeO₂ support, confirmed by atomic-scale electron microscopy characterization, which introduces additional degrees of freedom in coordination environment, chemical state, bond length, and strength. Combined with theocratical calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations, we confirmed that this “edge-interface” has distinct adsorption properties due to the change of O vacancy formation energy as well as the chemical states of Au resulting from the electron transfer and redistribution between the metal and the support. These results demonstrate a non-conventional geometric effect of rod-shaped supported metal catalysts on the catalytic performance, which could provide insights into the atomic-precise utilization of catalysts.