The production of polymer blend composites with distinctive characteristics is becoming increasingly popular worldwide due to the introduction of innovative properties. Polymer blend films comprising of PVA-CMC matrix doping with Ni0.8Mg0.2Fe2O4 (2,4,6, and 8 wt%) spinel ferrite nanoparticles were prepared using the solution casting method. The characteristics of the polymer films were analysed using X-ray diffraction (XRD), optical microscope (OM), roughness tester, Raman spectroscopy, and UV–vis spectroscopy. The synthesized of spinel ferrite Ni0.8Mg0.2Fe2O4 nanoparticles was confirmed by XRD and Raman spectroscopy. The powder's XRD pattern showed the presence of Ni0.8Mg0.2Fe2O4 in its cubic phase. Similarly, the diffraction pattern of the films confirmed the inclusion of Ni0.8Mg0.2Fe2O4 spinel ferrite nanoparticles in the PVA-CMC blend. The surface morphology analysis revealed an increase in the film roughness with increasing Ni0.8Mg0.2Fe2O4 concentration. Differential scanning calorimetry (DSC) explains that the system's thermal stability improves. The absorption edge shifted towards the higher wavelength region with the inclusion of Ni0.8Mg0.2Fe2O4 in PVA-CMC blend. Consequently, the optical bandgap values were observed to decrease from 5.50 eV to 3.89 eV and from 4.78 eV to 2.89 eV for direct and indirect transitions, respectively, as Ni0.8Mg0.2Fe2O4 increased from 0 to 8 wt%. The refractive index of the blend films increases from 1.776 for the pure blend to about 3.592, 6.142, 7.789, and 9.680 for 2, 4, 6, and 8 wt% Ni0.8Mg0.2Fe2O4 respectively. The optical conductivity was found to increase from 1.02 × 1011 to about 9.82 × 1012 S-1 for pure blend and PVA-CMC/8 wt% Ni0.8Mg0.2Fe2O4 films, respectively. Also, other optical parameters like optical basicity and electronegativity showed an enhancement with the incorporation of Ni0.8Mg0.2Fe2O4 nanoparticles in the PVA-CMC blend. The magnetic hysteresis plots of composites PVA-CMC/Ni0.8Mg0.2Fe2O4 exhibited ferromagnetic behavior characterized by a distinct magnetic hysteresis loop. © 2024 Elsevier B.V.