Pd−Pt core−shell nanoplates with hexagonal and triangular shapes were synthesized through the heterogeneous, epitaxial growth of Pt on Pd nanoplates. The Pd nanoplates were synthesized by reducing Na₂PdCl₄ precursor with PVP as a reducing agent, which then served as seeds for the nucleation of Pt atoms formed by reducing H₂PtCl₆ with citric acid. Characterization of the as-prepared Pd−Pt nanoplates by scanning transmission electron microscopy and high-resolution transmission electron microscopy reveals that a thin, uniform Pt shell was formed around the Pd nanoplate, demonstrating the layer-by-layer epitaxial growth of Pt on Pd surface in this approach. The close lattice match between Pd and Pt (lattice mismatch of only 0.77%) and the slow reduction rate associated with the mild reducing power of citric acid play key roles in achieving the epitaxial growth of Pt shells on Pd nanoplates.