This work reports the facile, controlled, and low-cost synthesis of a nickel oxide and polyaniline (PANI) nanocomposites-based electrode material for supercapacitor application. PANI-NiO nanocomposites with varying concentrations of NiO were synthesized via in-situ chemical oxidative polymerization of aniline. The XRD and FTIR support the interaction of PANI with NiO and the successful formation of the PANI-NiO-x nanocomposite. The SEM analysis showed that the NiO and PANI were mixed homogenously, in which the NiO nanomaterial was incorporated in porous PANI globular nanostructures. The multiple phases of the nanocomposite electrode material enhance the overall performance of the energy-storage behavior of the supercapacitor that was tested in 1 M H₂SO₄ using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the different nanocomposites, PANI-NiO-3 exhibit the specific capacitance of a 623 F g⁻¹ at 1 A g⁻¹ current density. Furthermore, the PANI-NiO-3 electrode retained 89.4% of its initial capacitance after 5000 cycles of GCD at a 20 A g⁻¹ current density, indicating its significant cyclic stability. Such results suggest that PANI-NiO nanocomposite could be proposed as an appropriate electrode material for supercapacitor applications.