By varying Co:Sb molar ratio, crystalline CoSb2O4 was synthesized through surfactant free hydrothermal method. The tetragonal crystal structure and phase composition of cobalt antimonate were obtained through XRD Rietveld refinement method. CoSb2O4 exhibits a direct band gap of 2.89 eV was computed using First-principle density functional theory (DFT) calculations. Here, the Fermi energy level is upshifted to conduction band region, representing the n-type behaviour of the CoSb2O4 unit cell. The oxidation state of +2 and + 3 of Co was identified through X-ray photoelectron spectroscopy analysis (XPS). Formation of submicron size, rod shape particles was confirmed by Transmission electron microscopic (TEM) images. Cyclic voltammogram exhibits a specific capacitance of 598 F g−1 at 2 mV s−1 in 1 M KOH. More importantly, Galvanostatic charge-discharge analysis (GCD) delivered the specific capacitance of 382 F g−1 at 1 mA cm−2. For practical application, an asymmetric supercapacitor is constructed using Ni3(Fe(CN)6)2(H2O) as a positive electrode and synthesized one-dimensional CoSb2O4 as a negative electrode, which offered a maximum specific capacitance of 279 Fg-1 at 1 mV s−1. Cycling stability of the fabricated device demonstrated the retention of almost 100% and hence depicts its promising nature as an efficient electrode for supercapacitor application.