Highly branched Pd-based nanocrystals are very attractive materials for electrocatalytic formic acid oxidation (FAO). Herein, a very simple synthetic method is proposed for preparing unique bi-metallic PdRu nanospine assemblies (PdRu NSAs) in high yield. The self-supported PdRu NSAs assembled by staggered nanospines show superior catalytic activity and durability for FAO, owing to their hyperbranched nanoarchitectures and bimetallic compositions. Different from the traditional multi-step routes, the proposed one-step synthetic method is very valuable for fabricating hyperbranched Pd-based catalysts with designed compositions and desired performances.