The effect of the solar irradiation on the structure and optical properties of Gafchromic films has been investigated for bio applications. Gafchromic (EBT2 series) films were exposed to different irradiation times (0–120 min) via a solar simulator under AM1.5 conditions. The structural variations of the prepared films were examined using FT–IR spectrophotometry. UV–visible-NIR spectra measurements were recorded to explore the optical properties. The absorbance spectra of the irradiated films increase as the irradiation time increases up to 120 min. The obtained optical bandgap of the prepared films decreases from 2.45 eV to–2.24 eV as the irradiation time increases from 0 to 120 min. Moreover, the increase in the irradiation time up to 120 min. results in an increase in the refractive index (n) and the dielectric constant values in the investigated UV–visible-NIR regions. According to our knowledge, this is the first time that the effect of the solar irradiation on the Gafchromic films has been investigated. Our novel results greatly recommend the use of the Gafchromic films (EBT2 series) in sensors, dosimetry and bio-applications.