In the present work, ceria-supported Au–Pt catalyst with metal ratio 3:2 was prepared using a “single-source precursor” concept. The double complex salt [AuEn2]2[Pt(NO2)4]3·6H2O was used as such precursor. CeO2 of unique morphology with developed surface area (120 m2/g) obtained by urea precipitation technique was used as a support. According to XRD data, size of the alloyed Au–Pt particles was estimated to be less than 3 nm. It was shown that bimetallic Au–Pt system intensifies release of oxygen from the CeO2 lattice. The 0.5%Au2Pt3/CeO2 catalyst was comparatively studied in low temperature CO oxidation (simplified model reaction mixture) and under prompt thermal aging conditions (complex reaction mixture) with regard to monometallic reference samples 0.2%Au/CeO2 and 0.3%Pt/CeO2. The catalytic performance of the samples was found to be significantly dependent on the reaction and pre-treatment conditions. In the case of the bimetallic catalyst, reversible redistribution and enrichment of the nanoparticle surface with Pt or Au were shown to be the key factor defining the activity.