This work is to explain the effect of illumination on optical properties of amorphous Ge₁₅In₅Se₈₀ films in the spectral range of 200–2500 nm. The spectral distribution of transmittance (T) for the as deposited and illuminated Ge₁₅In₅Se₈₀ films at different illumination times indicates a blue shift transmittance edge with exposure time (photobleaching effect). The dispersion data of the refractive index are analyzed using the concept of single oscillator model. Smakula׳s equation is used to calculate the concentration of color centers appear in the absorption curves. The increasing of energy gap with exposure time confirmed photoinduced bleaching in Ge₁₅In₅Se₈₀ films. The effect of illumination on the non-linear optical susceptibility (χ⁽³⁾) and non-linear refractive index (n₂) is calculated using empirical relations.