In this paper, Cu²⁺ doped ceria nanospheres were produced from a one-step hydrothermal synthesis. The products were characterized in detail at the structural and electronic level by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). XRD results revealed that the doped ceria was free of other crystallographic phases, such as CeOHCO₃, CuO or Cu₂O. By introducing various reactant molar ratios of Cu : Ce, the composition can be freely manipulated. The H₂-TPR measurement shows the improved reduction behaviour of the doped ceria samples prepared by us. A preliminary CO catalytic oxidation experiment indicated that the Cu²⁺ doped ceria samples showed strikingly higher catalytic activity, due to the intrinsic surface defects of the samples. In addition ceria doped with other transition metal ions (M²⁺), such Co²⁺, Ni²⁺ and Mn²⁺, has also been successfully prepared. Considering this one-step synthesis as a versatile approach, it can be further extended to other binary metal oxide systems.