In this study, Undoped and Cu-doped Ni0.6-x Zn0.4CuxFe2O4 (x = 0, 0.3) ferrite nanoparticles were synthesized using the sol-gel auto combustion method. The nanoparticles exhibited a single-phase spinel crystal structure as confirmed by XRD analysis. The crystallite sizes were determined to be in the range of 20 to 30 nm. SEM revealed the nanoparticles to have a spherical morphology. EDS confirmed the elemental composition and purity of the nanoparticles. FTIR analysis provided insights into the vibrational modes and bonding characteristics of the nanoparticles. UV-VIS was employed to investigate the optical properties of the nanoparticles, revealing band gap energies ranging from 2.80 to 3.5 eV. The photocatalytic activity of the nanoparticles was evaluated through the degradation of methylene blue under sunlight irradiation, demonstrating their effectiveness as photocatalysts. These findings contribute structural and optical properties of undoped and Cu-doped Ni-Zn ferrite nanoparticles, emphasizing their potential as efficient photocatalysts for environmental applications.