PtPd bimetallic nanodendrites (NDs), with enhanced activities from PtPd over element Pt and unique anisotropic morphology, show potential as catalysts in fuel cell applications. However, the research has been limited to pure materials, and constructing a practical fuel cell catalyst electrode from PtPd NDs still remains as a challenge. In this paper, we demonstrated, for the first time, catalyst electrodes from PtPd NDs for polymer electrolyte fuel cell (PEFC) applications. PtPd NDs are in-situ grown on large-area carbon paper gas diffusion layers (GDLs) and directly employed as cathodes in H2/air PEFCs. The thin catalyst layer with PtPd nanodendrites significantly reduces mass transfer resistance and a higher power performance is achieved than those based on pure Pt nanowires and Pt/C nanoparticle electrocatalysts. The crystal growth mechanisms of this advanced nanostructure on large-area support are also detailed based on the time-dependent experiments and Pd content.