Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu₃Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu₃Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu₃Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu₃Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors.