In this report, for the first time, we have applied green synthesis Ni0 nanoparticles (NiO-NPs) as an electrode material for supercapacitor (SC). Hydrangea paniculata flower extracts were used for the green synthesis of NiO-NPs. The green synthesized NiO-NPs is found to be 33 nm with surface area of 78.472 m(2) g(-1) along with pore volume and pore size of 0.149 cm(3) g(-1) and 4.061 nm. The green synthesized NiO-NPs based electrode exhibit high specific capacitance of 752, 709, 644, 603 and 581 F g(-1) at current densities of 2.5, 5, 10, 20, and 40 Ag-1, respectively, are revealing excellent capacitance retention even at a high current density. More notably, the NiO-NPs electrodes also show outstanding cycling stability up to 5000 cycles at 10 A g(-1) without discernable capacitance fading. This superior electrochemical performance of NiO-NPs is mainly attributed to the nano-dimention of the particles, which shorten the diffusion path lengths for both ions and electrons, ease migration during the rapid charge-discharge process and consequently improve the effective electrochemical utilization of electroactive material. (C) 2017 Elsevier B.V. All rights reserved.