In this study, copper-substituted cobalt nanocrystalline particles, CuxCo1-xFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) (CCFO) were synthesized using the sol-gel technique. The structural and phase properties were identified using X-ray diffraction (XRD). The single-phase cubic arrangement is apparent through the Rietveld refinement identified with the Fd3‾m space group. As the amount of Cu2+ doped increased, the average size of the crystallite ranged from 11 to 16 nm, as per the Debye Scherrer method. Performing High-Resolution Transmission Electron Microscopy (HRTEM) for the surface morphological assessments demonstrates that each sample is sphere-shaped and accurately prepared. UV–visible spectroscopy was used to examine the band gap reduction from 2.06 to 1.80 eV when the Cu2+ content ascended. The magnetic characteristics were analyzed using the Vibrating Sample Magnetometer (VSM) of the produced CCFO in the 5 K–300 K temperature range. The saturation magnetization, remanent magnetization, and coercivity changed gradually as the Cu2+ amount increased. According to the ZFC–FC magnetization curves, the synthesized nanoparticles exhibit ferrimagnetic behaviour at room and lower temperatures because their blocking temperature (TB) is higher than room temperature. It was found that the FC curves were almost flat just below TB, revealing spin-glass behaviour that could be explained by interactions between nanoparticles and surface effects, which include spin disorder and spin canting. According to the current study, variations in Cu present in cobalt nanoferrites can modify their structural, band gap, and magnetic characteristics for many applications in photocatalysis, dye degradation, magnetic resonance imaging, specific drug delivery, magnetic separation and memory devices.