Transition metal diselenides have been considered as one of the most promising earth-abundant electrocatalysts as alternatives to noble metal for the hydrogen evolution reaction (HER). Here, hierarchically three-dimensional nickel cobalt diselenides (Ni1/3Co2/3Se2) with networked nanowires and nanosheets characteristics have been successfully synthesized. Such morphological features may not only provide large surface area allowing for exposure of more active sites, but also benefit deep electrolyte penetration for electrons and electrolyte ions. The resulting binder-free flexible electrodes with large production yield exhibit superior electrochemical HER activity and excellent durability after potential sweep tests for 1000 cycles. Besides their catalytic activity remain stable for electrolysis over 8 h at mixed overpotential. The outstanding electrocatalytic performance makes the present nickel cobalt diselenide as a promising earth-abundant electrocatalyst for HER application. (C) 2016 Elsevier Ltd. All rights reserved.