This document describes the preparation and characterization of polyvinyl alcohol (PVA) composites with the addition of [Co(NH3)5Cl]Cl2 complexes. The composites were prepared by casting technique with different thicknesses and concentrations of the complex. Optical properties including absorption, absorption coefficient, extinction coefficient, refractive index, and dielectric constant were measured using UV-visible spectroscopy. The results showed that all optical properties increased with higher concentrations of the [Co(NH3)5Cl]Cl2 complex in the PVA composites.