Nickel-doped cerium oxide nanosphere@polyaniline (Ni-CeO2@PANI) was prepared through a facile two-stage synthetic method composed of hydrothermal and polymerized reactions. Addition of HCl affects the morphology control and electrochemical performance of Ni-CeO2@PANI nanocomposites. The nanocomposites were characterized using several techniques. With increasing amount of HCl, various shape-controlled nanocomposites, such as non-spacing core-shell Ni-CeO2@PANI nanospheres (NCP1), yolk-shell Ni-CeO2@PANI nanospheres, and PANI hollow spheres, were prepared. Ni-CeO2@PANI nanocomposites, as an electrode material, were fabricated into supercapacitors and characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge measurements. Results showed synergetic effects on NCP1, where capacitance and stability were derived from the PANI component and Ni-CeO2, respectively. This material exhibited high specific capacitance (866 F g(-1) at 1 A g(-1)), high energy density (120.3 Wh kg(-1)), and excellent cycling stability (85.6% remaining content after 10,000 number cycles).