Heterostructures consisting of distinct components have attracted considerable attention due to their unique properties and promising applications in catalysis enabled by the synergistic effect among different components. [1][2][3][4][5] Since phase engineering of nanomaterials (PEN) provides various strategies to rationally design and synthesize nanomaterials with novel crystal phases, [6] the delicate modu lation of crystal phases of each component in heterostructures with diverse morpho logies becomes possible, which is of great importance to realize tunable physical and chemical properties and enhanced perfor mances. In addition to controlling their compositions, morphologies, architec tures, facets, sizes, and dimensionalities, tremendous efforts have been devoted to constructing heterostructures con sisting of different phases during recent years. For example, highly luminescent CdSe/CdS heterostructure with tetrapod Phase engineering of nanomaterials (PEN) offers a promising route to rationally tune the physicochemical properties of nanomaterials and further enhance their performance in various applications. However, it remains a great challenge to construct well-defined crystalline@amorphous core-shell heterostructured nanomaterials with the same chemical components. Herein, the synthesis of binary (Pd-P) crystalline@amorphous heterostructured nanoplates using Cu 3−χ P nanoplates as templates, via cation exchange, is reported. The obtained nanoplate possesses a crystalline core and an amorphous shell with the same elemental components, referred to as c-Pd-P@a-Pd-P. Moreover, the obtained c-Pd-P@a-Pd-P nanoplates can serve as templates to be further alloyed with Ni, forming ternary (Pd-Ni-P) crystalline@amorphous heterostructured nanoplates, referred to as c-Pd-Ni-P@a-Pd-Ni-P. The atomic content of Ni in the c-Pd-Ni-P@a-Pd-Ni-P nanoplates can be tuned in the range from 9.47 to 38.61 at%. When used as a catalyst, the c-Pd-Ni-P@a-Pd-Ni-P nanoplates with 9.47 at% Ni exhibit excellent electrocatalytic activity toward ethanol oxidation, showing a high mass current density up to 3.05 A mg Pd −1 , which is 4.5 times that of the commercial Pd/C catalyst (0.68 A mg Pd −1 ).