Abstract <p>The results of a study of the initial stage of carbonization process of a polyimide film when treated with a Nd:YAG laser with a wavelength of λ = 1064 nm are presented. Under the influence of laser radiation, thermal destruction of the material occurs accompanied by profound changes in the polymer chain, the release of volatile products, and the formation of numerous small bubbles within the film. In the processed samples, local areas of darkening are found related to changes in the structure of the initial material leading to a decrease in transparency of the initial film. The transparency of the films after laser processing is determined using high-resolution spectrometers in the visible and near infrared spectral regions. It is shown that the key processing parameters—radiation power and beam scanning velocity (processing time)—have a decisive influence on the chemical transformation of polymer chains and the intensity of gas formation in the volume of polyimide films. The energy impact of laser radiation is assessed using the dynamic energy density parameter of laser radiation <i>H</i>. It is established that minimum value of energy density, at which the process of chemical transformation of the structure begins with the formation of darkening areas and the emergence of gas bubbles in the structure of the samples is <i>H</i> = 0.42 J/mm². With an increase in energy density to a value of <i>H</i> = 2.10 J/mm², the film is destroyed with the formation of local through-holes, and when the value of <i>H</i>&#xa0;= 2.85 J/mm² is reached, complete ablation of the material in the processing area is observed.</p>