A facile and fast approach for the synthesis of a nanostructured nickel hydroxide (Ni(OH)2) via sonochemical technique is reported in the present study. The X-ray diffraction results confirmed that the synthesized Ni(OH)2 was oriented in β-phase of hexagonal brucite structure. The nanostructured Ni(OH)2 electrode exhibited the maximum specific capacitance of 1256F/g at a current density of 200mA/g in 1M KOH(aq). Ni(OH)2 electrodes exhibited the pseudocapacitive behavior due to the presence of redox reaction. It also exhibited long-term cyclic stability of 85% after 2000 cycles, suggesting that the nanostructured Ni(OH)2 electrode will play a promising role for high performance supercapacitor application. Display omitted •Nanostructured nickel hydroxide was synthesized via one step process.•The non-aggregated β-phase of hexagonal brucite structure was observed.•It exhibited maximum specific capacitance of 1256F/g at 200mA/g.•It exhibited long-term cyclic stability of 93% after 1000 cycles.