Palladium and rhodium are known to be partly miscible metals. In present work, the peculiarities of coordination compound [Pd(NH3)(4)](3)[Rh(NO2)(6)](2) decomposition with formation of nanosized solid solutions under different atmospheres were studied by means of thermal gravimetry. Formation of alloy nanoparticles were confirmed by powder X-ray diffraction analysis, scanning and transmission electron microscopies. A bimetallic Pd-Rh/alumina catalyst was prepared by incipient wetness impregnation using coordination compound [Pd(NH3)(4)](3)[Rh(NO2)(6)](2) as a precursor. Monometallic reference samples were obtained using [Pd(NH3)(4)](NO3)(2) and Na-3[Rh(NO2)(6)], correspondingly. Catalytic performance and stability of the catalysts were examined in a model reaction of CO oxidation in a prompt thermal aging regime. The environment of precursor decomposition was shown to affect noticeably both the initial activity and stability of the samples in the studied reaction. Reductive atmosphere in comparison with inert and oxidative ones facilitates the formation of the smallest active component species, which demonstrate highest initial activity but worst stability.