<p>The incorporation of Zn_0.1Co_0.9Fe₂O₄ nanoparticles into poly (methyl methacrylate) (PMMA) and its effects on the structural and optical properties of the resulting nanocomposite have been studied. Comprehensive analyses, including X-ray diffraction and Fourier-transform infrared spectroscopy, reveal significant alterations in the structural characteristics of PMMA due to the integration of the nanofiller, suggesting enhanced material complexity. Notably, optical parameters such as oscillator energy, refractive index, high-frequency dielectric constant, Relaxation time, Optical plasma frequency, and optical mobility were systematically evaluated across varying concentrations (1%, 2%, and 5%) of Zn_0.1Co_0.9Fe₂O₄, highlighting a marked reduction in direct optical band gap energy with increasing nanoparticle concentration. This reduction is attributed to a rise in charge carrier concentration and increased absorption in the UV Region, which enhances the optical conductivity and UV shielding properties of the PMMA/Zn_0.1Co_0.9Fe₂O₄ composites. The findings indicate that the doped materials exhibit elevated refractive indices and dielectric constants, suggesting their suitability for applications in solar coatings, energy storage devices, and optoelectronic devices. Further exploration of varying nanoparticle concentrations could yield deeper insights into the potential of PMMA-based nanocomposites across diverse fields for energy applications.</p>