In this study, we examined into the synthesis of nickel ferrite (NiFe2O4) nanoparticles utilizing the sol-gel auto-combustion method, followed by heat treatment at different temperatures. The structural properties of NiFe2O4 were found to be a spinel structure with the space group Fd-3m and a face-centered cubic arrangement. The crystallites size and lattice parameter increased, while the density decreased. SEM was utilised to analyse the surface structure morphology of the synthesised NiFe2O4 nanoparticles. The functional groups and their accompanying strong absorption bands at 534 cm−1 and 375 cm−1 were identified using Fourier transform infrared analysis (FTIR). The sample's optical absorbance was measured between 200 to 800 nm, and the size of the bands detected in the test sample was subsequently investigated. This study examines the ultraviolet (UV) area, specifically the energy band gap (Eg) values of 2.1 and 2.21 eV. The aforementioned technology has a wide range of applications in the areas of electromagnetic wave absorbers, electrodes, sensors, and magnetic recording media devices.