<p>This present study focuses on the synthesis, characterization, and evaluation of the role of copper sulfate (CuSO₄) in the structure and optical properties of carboxymethyl cellulose (CMC) and sodium alginate (SA) polymer composite in a 50:50 (wt%). Polymer composite thin films were produced via the casting/solvent evaporation method with varying filled concentrations of <i>x</i>CuSO₄ (<i>x</i> = 0, 0.1, 0.3, 0.6, and 0.9 wt%). Structural analysis was conducted utilizing several techniques. The XRD patterns have showed that the CMC/SA blend sample had an amorphous nature, whereas CMC/SA samples containing CuSO₄ exhibited a polycrystalline structure. FTIR experimental data revealed the vibrations associated with the two polymer groups and confirmed the formation of interaction among the Cu and S in the natural polymers. The UV–Vis results showed that the 0.9 Cu sample exhibited a higher maximum absorption capacity than the other synthesized thin films. Different optical parameters, namely optical energy gap, refractive index, electronic polarizability, optical dielectric constant, and dielectric loss, have been calculated. The energy gap (<i>E</i>_g) values were decreased with increasing CuSO₄ content. The refractive index values were estimated to be between 2.26 and 2.36, and the reflection loss to be between 0.150 and 0.165. The mass attenuation coefficient (<i>μ</i>ₘ) for gamma ray in the energy range of 0.001–1.5&#xa0;MeV was investigated utilizing the theoretical calculation program (XCOM), and the result revealed that <i>μ</i>ₘ (in micrometers in cm²/g) values are 0.083, 0.0624, and 0.0588 cm²/g, for 662, 1173, and 1332&#xa0;keV gamma ray energies, respectively. Based on the obtained results, the synthesized polymer thin films can potentially be used as UV protection functional films for fruit and food packaging.</p>