Structurally ordered phase of PdCu₃ nanoparticles (NPs)/carbon black (CB), in which PdCu₃ has a Cu₃Au-type structure, was prepared by co-reduction of Pd and Cu precursor using ethylene glycol as reducing agent and annealing procedure. The obtained catalysts were characterized by using X-ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The XRD and STEM measurements allowed us to confirm the crystal structures of both atomically disordered Pd-Cu NPs/CB and ordered intermetallic PdCu₃ NPs/CB. From the TEM and EDS measurements, it was found that PdCu₃ NPs are uniformly dispersed on the CB surface and the atomic ratio of Pd and Cu is 25.3 : 74.7. The DFT calculations suggested that the as-prepared PdCu₃ NPs have a uniformly ordered structure of Pd and Cu atoms without segregation of Pd and/or Cu, while the Cu-free surface structured PdCu₃ NPs, which are formed by a so-called electrochemical dealloying, i.e., the surface and sub-surface Cu dissolution from the PdCu₃ ordered structure, possess a superior electrocatalytic activity for the ORR compared with Pd NPs/CB. This catalytic activity can be explained reasonably based on the measured d – band center value and the theoretical calculation of catalyst – oxygen binding energies. In addition, a possibility of PdCu₃ NPs/CB as a cathode catalyst in direct methanol fuel cells is discussed briefly.