In this work, we report the synthesis of Ni nanoparticles encapsulated in carbon nanotubes (CNTs) by a facile and novel one-step pyrolysis method which are obtained from fumaric acid and nickel acetate as carbon and nickel sources respectively. The synthesized Ni encapsulated CNTs were characterized by various methods and were confirmed to possess large surface areas and numerous mesopores, they were applied as non-precious metal electrocatalyst for HER in 1 M KOH solution. The results show that the Ni encapsulated carbon nanotubes synthesized at 650 degrees C exhibited the best catalytic activity and stability with the smallest Tafel slope of 102 mV dec(-1), an onset potential of 110 mV and over-potential of 266 mV to achieve a current density of -10 mA cm(-2). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.