The present work deals with the synthesis of nanostructured Co-MgO mixed oxides with different weight ratios of cobalt by a facile co-precipitation method as a catalyst for low-temperature CO oxidation. The prepared samples were characterized by X-ray diffraction (XRD), N-2 adsorption/desorption (BET), Fourier transform infrared spectroscopy (FTIR), and transmission and scanning electron microscopies (TEM and SEM) techniques. The results revealed that inexpensive cobalt-magnesium mixed metal oxide nanoparticles have a high potential as catalyst in low-temperature CO oxidation. The Co-MgO mixed oxide with 30 wt.% cobalt had the highest activity. The results showed that the catalysts pretreated under O-2-containing atmosphere possessed higher activity compared to the catalyst pretreated under H-2 atmosphere. Co-MgO catalyst showed a good repeatability in reaction condition. The stability test exhibited that the Co-MgO mixed oxides were highly stable for CO oxidation over a 30 h time on stream in the feed gas containing a high amount of moisture and CO2.