Ternary I-Cu2WS4 were synthesized based on hot-injection process and their thin films are prepared by spin coating techniques at ambient temperature. The energy dispersive analysis of X-rays of the thin films confirmed that synthesized thin film is stoichiometric. Transmittance and reflectance have been used to determine the optical, dispersion and dielectric properties of the Cu2WS4 in the range of 200–2400 nm. The transparency of the Cu2WS4 is 40–45% in the visible range. Optical dispersion parameters have been calculated by using the single term Sellmeier dispersion relation and Wemple–DiDomenico single oscillator model. Several dispersion parameters were determined by the analysis of refractive index dispersion.Absorption coefficient (α), extinction coefficient (k), the Urbach energy (EU), real and imaginary parts of dielectric constant (ε) and surface and volume energy loss function have been calculated. The optical bandgap determined by the optical absorbance spectrum analysis showed that thin films possess a direct bandgap of 1.74 eV.