In the progress work, the facile microwave method has been used to synthesize BiI3 nanoparticles at low temperatures, while nanocomposite films based on polyvinyl alcohol (PVAL) filled with selective content of BiI3 nanoparticles (from 0 to 18.51 wt %) have been prepared by casting technique. The structural analysis has been analyzed by X-ray diffraction, EDX (energy dispersive analysis spectroscopy of X-rays), HR-TEM (High-resolution transmission electron microscope), and atomic force microscope (AFM) measurements. The thermal behavior such as DTG (derivative thermogravimetric) and TGA (thermogravimetric analysis) of BiI3/PVAL nanocomposite was also studied. At the same time, the optical performance of these films was measured using UV–Vis–NIR spectroscopy. The structure study shows significant incorporation between the two phases of PVAL and BiI3 in all films. The AFM images show an increase in surface roughness with the nanoparticle content. The BiI3 level has influenced optical parameters like the energy of the band tail, the energy gap, the absorption coefficient, and the dielectric loss of the PVAL matrix. 18.51 wt % BiI3/PVAL film has a direct transition with the lowest energy gap, while its higher absorbance is due to the increase of the influence of the crystalline phases of BiI3 in the polymeric matrix. The strong competence of the films to reduce the power of the two laser beams (632.8 nm & 533 nm) has been detected. Therefore, the results support that this nanocomposite is a fruitful material for commercial laser cut-off and optoelectronics.