The casting technique was used to fabricate carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), and PVA/CMC blend films. The sensitivity of the prepared films to irradiation was examined by applying gamma radiation with an intensity of 100 kGy. Structural and optical properties of unirradiated and gamma-irradiated films were investigated using Fourier-transform infrared (FTIR) and UV–Vis spectroscopy, respectively. Photoluminescence spectra were recorded for polymer films before and after exposure to gamma rays. The PVA film has a higher transmittance than the CMC film and PVA/CMC blend films. Moreover, the film’s transmittance decreases when exposed to 100 kGy gamma rays, especially in the UV region. The optical bandgap (Eg) values are 5.75 eV and 5.60 eV for pure PVA and pure CMC, respectively. While for blended films it is lessened to about 5.50 eV for PVA–12%CMC blend film. Moreover, these values are slightly decreased after irradiation with gamma-ray to about 5.70, 5.55, and 5.45 eV for pure PVA, pure CMC, and PVA–12%CMC blend films. While the refractive indices values are 1.965, 2.024, and 2.355 for pure PVA, pure CMC, and PVA–12%CMC blend, respectively. These values decreased after exposure to gamma-ray to about 1.959, 2.016, and 2.256 for pure PVA, pure CMC, and PVA–12%CMC blend, respectively. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.