A Radiochromic film dosimeter for gamma radiation was prepared from polyvinyl alcohol (PVA) and methyl red (MR) by condensation polymerization. To confirm the reaction, the obtained PVA-MR film was characterized by Fourier-transform infrared spectroscopy (FTIR) and compared to PVA film. The result shows the appearance of new vibrational stretching at ∼1700 cm-1, related to carbonyl groups, indicating that the reaction between PVA and MR has been successfully done. The effect of radiation on the color change characteristic of PVA-MR film and its possibility to be used as a radiochromic film dosimeter were investigated using ultraviolet (UV)-Vis spectrophotometry. The absorption spectrum of PVA-MR can be seen in the visible region at ∼420 nm, which is characteristic of red, and the film undergoes decolorization gradually from red to transparent when exposed to gamma radiation up to 100 kGy. Moreover, the response of these dosimeters at different times after irradiation was tested and the energy band gap, Eg, was also calculated. © Published under licence by IOP Publishing Ltd.