Due to the scarcity of Pt, it is highly desirable to construct core-shell structures with ultrathin Pt shells while maintaining their high electrocatalytic activities. However, it is necessary to preferentially synthesize a core with a specific structure before further formation of core-shell catalysts with specific morphologies. This prerequisite greatly increases the complexity of the synthesis process. This article describes a synthetic method of core-shell Pd@Pt octahedra catalysts from Pd nanocubes, truncated nanocubes or truncated octahedra. The formation of octahedral core-shell structures involves two key factors: (1) the oxidative etching process of Pd atoms at the corner sites; (2) the different reduction rates between Pt and Pd precursors. This mechanism can be extended to synthesize carbon-supported sub-8 nm Pd@Pt octahedra from commercial Pd/C catalysts. The derived carbon-supported Pd@Pt octahedra catalysts performed comparable activity and durability for methanol oxidation reaction with state-of-art PtRu/C catalysts. This synthetic method provides an innovative path for large-scale production of well-controlled catalysts. (c) 2017 American Institute of Chemical Engineers AIChE J, 63: 2528-2534, 2017