The effect of particle size and morphological structure on the electrical and electrochemical properties of ZnO (nanowires, nanorods, and nanospheres) prepared by two various routes: soft-wet and dry methods were investigated. The electrochemical performance is analyzed by cyclic voltammetric and galvanostatic charge–discharge measurements in 1 M KOH, whereas their electrical conductivity, and dielectric constant are measured by electrochemical impedance spectroscopy in a temperature range 293–383 K and frequencies from 102 to 107 Hz. All samples showed semiconducting behavior with conductivity values depending on the particle size and the morphological structure of the sample. The prepared samples showed supercapacitance behavior with capacitance values lie between 77 and 330 F g−1 and depend upon the morphological structure. The nanowire's structure showed the highest capacitance and good cycling stability. The high performance depends on the nanocrystalline size and the high surface area of the nanowire sample.