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A CeO 2 -based heterostructure nanocomposite has been attractive as an electrode material for energy storage and as an electrochemical sensor. In the present work, a CeO 2 @NiO nanocomposite was prepared by a simple hydrothermal method. The structural and morphological information on the heterostructure CeO 2 @NiO nanocomposite were obtained by using different characterization methods like X-ray diffraction, UV-visible, Fourier transform infrared, electron paramagnetic resonance, Raman, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray elemental color mapping, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Compared with pristine CeO 2 , the heterostructure CeO 2 @NiO nanocomposite exhibits a higher electrochemical performance with a specific capacitance of 317 F g -1 at a current density of 1 A g -1 in a 1 M KOH electrolyte. This device demonstrates a high energy density and a power density of 11 Wh kg -1 and 750 W kg -1 , respectively. Besides, it was found that CeO 2 @NiO/glassy carbon electrode (GCE) shows appreciable electrocatalytic activity toward NO 2 - oxidation. The CeO 2 @NiO-modified electrode displays a linear response for NO 2 - oxidation between 0.001 × 10 -6 and 4 × 10 -3 M. Apart from high sensitivity (2260 μA mM -1 cm -2 ), the CeO 2 @NiO-modified electrode also exhibits good selectivity and long-term stability for nitrite (NO 2 - ) detection in a water real sample, and the obtained results showed excellent recovery. The encouraging electrochemical performance of the CeO 2 @NiO nanocomposite provides a promising approach for the development of multifunctional electrode materials for future energy storage devices and sensors.