Hybrid nanostructures can combine two or more functionalities in one unit and oftentimes exhibit synergistically enhanced properties compared to the simple sum of the constituents. Herein, we demonstrate the facile synthesis of Pt–CuS heterogeneous nanoparticle dimers based on the sulfidation of the corresponding bimetallic alloy templates. It begins with the preparation of CuPt alloy nanoparticles in an organic solvent, which are then converted into Pt–CuS heterodimers by reacting with elemental sulfur in octadecene at elevated temperatures. The Pt–CuS heterodimers display highly selective activity for catalyzing the methanol oxidation reaction at room temperature due to the strong electronic coupling effect between the different domains in the heterodimers. The structural transformation from alloy to heterogeneous nanomaterials may provide new opportunities to design and fabricate hybrid nanostructures with interesting physicochemical properties.