We describe the fabrication of novel PdCu bimetallic nanocomposites with hierarchically hollow structures through a simple galvanic replacement reaction using dealloyed nanoporous copper (NPC) as both a template and reducing agent. The reaction process was monitored by UV−vis absorbance spectra and X-ray diffraction (XRD), which clearly demonstrate a structure evolution from NPC precursor to a Pd-rich PdCu alloy structure upon the completion of the reaction. Structure characterization by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) indicates that the replacement reaction between NPC and [PdCl₄]²⁻ solution results in a nanotubular mesoporous structure with a nanoporous shell, which is comprised of interconnected alloy nanoparticles with size around 3 nm. The resulted PdCu nanostructure shows superior activity toward oxygen reduction reaction (ORR) with a half-wave potential at 0.840 V, which is significantly better than that of the commercial Pt/C catalyst.