SnO2 was prepared by the hydrothermal route. Aniline monomer was polymerized in the suspension of SnO2 to form inorganic–organic nanocomposite materials, in which SnO2 particles were embedded within polyaniline (PANI). Morphological and structural characterizations of the prepared samples were carried out using scanning electron microscope; transmission electron microscope; power X-ray diffraction and Fourier transform infrared spectroscopy. Their electrochemical properties were also investigated using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The as-prepared nanocomposites had excellent properties in the capacitance, and its specific capacitance was up to 501Fg−1 with a specific energy density of 66.8Whkg−1 at a power density of 960.6Wkg−1. The device fulfilled the requirement of long durability necessary for an energy storage system, since after 2000 galvanostatic charge–discharge cycles, retention of 85.8% in capacitance was observed. These results indicated that the PANI/SnO2 had a synergistic effect of the complementary properties of both components.