A fast one-step co-reduction method was developed to synthesize trimetallic PtCoNi alloyed flower-like networks (PtCoNi FNs) in an ice-bath only using KBH4 as the reductant, while no any polymer, seed, organic or surfactant was involved. The morphology, structure and composition of the product were characterized by microscopic analysis, X-ray diffraction and X-ray photoelectron spectroscopy. The architectures exhibited boosted electrocatalytic activity and stability for hydrogen evolution reaction (HER) in acidic and alkaline media. The overpotential of PtCoNi FNs for HER is smaller than the contrast materials (PtCo NPs, PtNi NCs, Pt black and Pt/C) at the fixed current density of 10 mA cm(-2), and the correlative exchange current density is significantly enlarged compared with commercial Pt black while comparable to commercial Pt/C (20 wt%). Besides, the catalyst showed the highly boosted catalytic characters for oxygen reduction reaction (ORR) with the more positive onset potential and faster kinetics. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.