The fabrication of thin films of unexposed and irradiated indium chloride phthalocyanine (lnPcCl) was achieved through vacuum thermal evaporation. Analysis via X-ray diffraction confirmed that both types of films exhibited an amorphous structure. Optical properties were examined between 300 and 2500 nm. The impact of gamma radiation doses was evident in the reduction of optical and fundamental band gap energies, with optical transitions being indirect. Evaluation of dispersion parameters, including oscillator energy (E0) and dispersion energy (Ed), using the Wemple and DiDomenico method revealed their augmentation with increasing gamma doses. Moreover, the nonlinear optical parameter increased, corresponding to higher gamma doses. This underscores the technique's efficacy in enhancing the optical characteristics of lnPcCl. The observed decrease in the optical band gap energy and the heightened nonlinear optical parameters underscore the potential of this material for various optical applications, including but not limited to solar cells, optoelectronic devices, and nonlinear optical devices.