Pt-based bimetallic nanostructures have found intriguing applications in electrocatalysis. However, the pristine Pt-based nanostructures generally lack the selectivity for the target reaction because of their high activity for both oxygen reduction reactions (ORRs) and fuel molecule oxidation reactions. By employing a recently developed chemical functionalization strategy, the functionalized Pt-based nanostructures have achieved their selectivity for the target reaction in fuel cells. In this work, we report a facile thermal decomposition route to synthesize the polyallylamine (PAH)-functionalized Pd–Pt bimetallic core–shell nanodendrites with a Pd-rich PdPt alloy core and a Pt-rich PtPd alloy shell (PdPt@PtPd CSNDs) by using PAH that serves as a complexant, reductant and chemical functionalization molecule. The composition, morphology and structure of PdPt@PtPd CSNDs are characterized in detail. Compared with commercial Pt black electrocatalyst, the PAH-functionalized PdPt@PtPd CSNDs show improved electrocatalytic activity and durability for the ORR, and achieve good selectivity for the ORR in the presence of ethanol molecules. The study shows a promising cathode electrocatalyst for direct alcohol fuel cells (DAFCs). Palladium–platinum core–shell nanodendrites have been made that are promising as a cathode electrocatalyst for direct alcohol fuel cells. Such fuel cells convert the chemical energy of alcohol into electricity and are attractive for powering vehicles and portable electronic devices. To become commercially viable, it is vital to improve the efficiency, activity, alcohol tolerance and durability of platinum electrocatalysts for the oxygen reduction reaction (ORR). Now, researchers in Singapore and China have demonstrated a simple one-step approach involving water-based thermal decomposition for synthesizing polyallylamine-functionalized palladium–platinum nanodendrites that have palladium-rich cores and platinum-rich shells. These bimetallic nanostructures exhibited superior electrocatalytic activity and durability for the ORR than a commercial platinum black electrocatalyst. Importantly, unlike pristine platinum-based nanostructures, they showed good selectivity for the ORR in the presence of ethanol. The polyallylamine functionalization imparted Pd–Pt nanodendrites with extraordinary selectivity for the oxygen reduction reaction because of its steric hindrance effect and ethanol-phobic property.