Alloying platinum with a second metal such as palladium can increase the mass activity of Pt and lower the usage of expensive Pt elements, hence is of great importance for designing highly efficient and cost-effective electrocatalysts for oxygen reduction reaction (ORR). In this study, monomorphic PtPd alloyed worm-like nanoparticles (PtPd WNPs) with dominant (111) facets were prepared with a facile one-pot approach. The detailed morphology, composition, and surface structure of the PtPd WNPs were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), X-ray diffraction (XRD), as well as Xray photoelectron spectroscopy (XPS). The prepared PtPd WNPs displayed enhanced electrocatalytic activity and remarkably robust stability toward ORR in both alkaline and acidic media, superior than commercial Pt/C catalysts. This strategy may open a new route to design and prepare advanced electrocatalysts for fuel cells. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.