The development of cathode oxygen reduction reaction (ORR) catalysts with high characteristics for practical, direct methanol fuel cells (DMFCs) has continuously increased the attention of researchers. In this work, interface-rich Au-doped PdBi (PdBiAu) branched one-dimensional (1D) alloyed nanochains assembled by sub-6.5 nm particles have been prepared, exhibiting an ORR mass activity (MA) of 6.40 A·mg_Pd⁻¹ and long-term durability of 5,000 cycles in an alkaline medium. The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C (0.14 A·mg_Pt⁻¹) and Pd/C (0.08 A·mg_Pd⁻¹). The MA of binary PdBi nanochains also reaches 5.71 A·mg_Pd⁻¹. Notably, the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance. In actual DMFC device tests, the PdBiAu nanochains enhance power density of 140.1 mW·cm⁻² (in O₂)/112.4 mW·cm⁻² (in air) and durability compared with PdBi nanochains and Pt/C. The analysis of the structure—function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure, improved charge transfer capability, downshift of the d-band center of Pd, as well as the synergistic effect derived from “Pd-Bi” and/or “Pd-Au” dual active sites.