A set of three catalysts (a Au–Ni bimetallic and their corresponding Au and Ni monometallics) has been prepared by impregnation of previously prepared suspensions of monodisperse metallic particles to ensure the precise control of their physicochemical characteristics (size and composition). The Au–Ni/CeO2 bimetallic catalysts present better reactivity toward CO oxidation than monometallic Au/CeO2 and Ni/CeO2 prepared under identical conditions. “operando-like” characterization of Ni and Au atoms into the bimetallic particles using, among other techniques, ambient-pressure photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy has allowed us to determine that under oxidative conditions the samples present a Au@NiO core–shell distribution, where Ni surface atoms are affected by an electronic effect from inner Au atoms.