The heterobimetallic 15-MC-5 metallacrown of formula [CeCu₅(5mpzHA)₅(NO₃)(H₂O)₇]·2NO₃·7H₂O, designated MC-Ce, was synthesized using 5-methyl-2-pyrazinehydroxamic acid (5mpzHA) as a linker, reacting with Ce^III and Cu^II salts under mild conditions. Single-crystal X-ray diffraction analysis reveals a crown-like [Cu₅Ce(5mpzHA)₅] core, characteristic of a 15-MC-5 system, with five Cu^II atoms at the rim of the crown and the Ce^III ion occupying the dome of the crown, with water molecules, oxygen atoms and one nitrate anion filling the nine-coordination sphere around the Ce^III ion, which exhibits a distorted spherical tricapped trigonal prism geometry. The thermogravimetric analysis evidences successive mass losses due to the removal of water molecules and decomposition of the structure after 217 °C, whereas the PXRD analysis of the thermal decomposition residue reveals the presence of copper and copper/cerium oxide particles. These nanocomposite materials were also synthesized using the metallacrown MC-Ce under a hydrothermal method in the presence of multi-walled carbon nanotubes (MWCNTs), affording insights that this metallacrown can act as a source precursor for the synthesis of these mixed cerium/copper oxide nanomaterials. The experimental χMT value in MC-Ce at room temperature is 3.175 cm³ mol⁻¹ K, which is higher than the calculated one for one magnetically isolated Ce^III plus five Cu^II ions, probably due to the antiferromagnetic interactions among Cu^II ions within the metallacrown hoop plus the thermal depopulation of JZ sublevels of Ce^III ground state (5/2), which exhibit a small splitting under the anisotropic ligand field effects. The χMT decreases continuously until it reaches the value of 0.80 cm³ mol⁻¹ K at 10 K, reinforcing the presence of intramolecular antiferromagnetic interactions.