Nanosized zinc ferrite (ZnFe₂O₄) particles are prepared by a simple aspartic acid assisted combustion method at three different pH conditions. X-ray diffraction analysis (XRD) is used to identify the single phase formation of ZnFe₂O₄ and its crystal system. The particle size and shape are revealed through transmission electron microscopy (TEM) images and the particles are in the size range between 20–30 nm. The valence states of zinc, iron and oxygen are determined through X-ray photoelectron spectroscopy (XPS). The electrochemical performances of the individual electrodes and fabricated cells are studied using cyclic voltammetry (CV), galvanostatic charge–discharge analysis (GCD) and impedance spectroscopy (EIS) analysis. A maximum specific capacitance of 1235 F g⁻¹ at 1 mA cm⁻² is obtained for ZnFe₂O₄ prepared at pH 10. Furthermore an asymmetric supercapacitor (ASC) is fabricated using ZnFe₂O₄ as the negative electrode and Ni(OH)₂ as the positive electrode. Interestingly, this assembled ASC delivers good energy and power densities of 33 W h kg⁻¹ and 68 W kg⁻¹, respectively.