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.