The temperature dependent morphological evolution and its effect on the electrochemical supercapacitive properties of Ni(OH)₂ thin films have been systematically investigated. A temperature dependent growth mechanism model is proposed for the changes in microstructure. Different nanostructures of Ni(OH)₂ thin films such as nanoplates, stacked nanoplates, nanobelts and nanoribbons have been fabricated by varying the deposition temperature. An X-ray diffraction study discloses the orientations of different nanostructures and the formation of nanocrystalline β-Ni(OH)₂. Further, these Ni(OH)₂ nanostructures demonstrate excellent surface properties like uniform surface morphology, good surface area, pore volume and uniform pore size distribution. The electrochemical supercapacitive properties of Ni(OH)₂ nanostructures have been investigated by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy techniques. The electrochemical studies of the Ni(OH)₂ samples show an obvious influence of surface properties on the pseudocapacitance. The maximum specific capacitance of 357 F g⁻¹ was evaluated for nanoplates at a scan rate of 5 mV s⁻¹. Furthermore, all these Ni(OH)₂ samples show good long-term cycling performances in KOH electrolyte. The Ragone plots ascertain good power and energy densities of all Ni(OH)₂ nanostructured samples. Subsequently, electrochemical impedance measurements for the different nanostructures of Ni(OH)₂ electrodes are assessed indicating that the Ni(OH)₂ nanoplates structured electrodes are suitable for good capacity electrochemical supercapacitors.