In this study, a new 3D hierarchical Ni-CNT nanostructure was fabricated using electrodeposition method in a bath containing crystal modifier, where its electrocatalytic activity and stability for hydrogen evolution reaction (HER) were investigated. The resulting Ni-CNT nanostructures were characterized by different analysis such as XRD, SEM, EDS and AFM. The electrocatalytic activity, stability and corrosion resistance of the fabricated Ni-CNT as cathode for the HER in 1.0 M potassium hydroxide (KOH) solution were investigated by LSV curves, CV and EIS techniques. The results indicated highly active surface area as well as increased electrical conductivity owing to introduction of CNT into the Ni nanocones (NNCs) improving intrinsic catalytic activity for HER. Furthermore, due to their hierarchical structure, the Ni-CNT nanostructure facilities bubble detachment, effectively reducing the dead area resulted from bubbles phenomena. These two features are beneficial for high activity and stability during HER. This electrode able to afford current densities of 10, 20 and 100 mA/cm(2) at the HER overpotentials of 82 and 116 and 207 mV, respectively. High chemical stability of CNT leads to an increase in the electrocatalytic stability and corrosion resistance of Ni-CNT hierarchical nanostructure. This research introduces the novel 3D nanocomposite structure for enhancing electrocatalytic activity for HER.