Nanocomposite films of PVA and Cd0.9Mn0.1S prepared via solution casting method were exposed to different doses of gamma radiation. Several techniques have been applied to emphasis the effects of gamma ray on the properties of the nanocomposite sample. Induced structural changes were investigated by x-ray diffraction (XRD) and Fourier transform infrared (FTIR), whereas UV-vis spectroscopy and differential thermal analysis (DTA) were used to study irradiation effects on the optical and thermal properties of samples, respectively. XRD and FTIR revealed that the structure of samples is strongly affected upon irradiation and the crossliniking is the dominant process. The estimated values of the optical energy gap, Eg, Urbach energy, EU, and different optical parameters exhibited dose dependence. The direct optical energy gap of the pristine sample is about 5.47 eV, and decreases with irradiation to a value of 2.9 eV for 120 kGy irradiated sample. The observed increase in refractive index and Urbach energy with irradiation confirmed the reduction in the ordered structure of the samples because of crosslinking. The color difference between the irradiated samples and the pristine one, E, increases from 1.6 to 73.8 with increasing the gamma dose. DTA data indicates that increasing dose decreases melting point, which can be attributed to defects generation by irradiation.