Poly(3,4‐ethylenedioxythiophene):poly(styrenesulphonate) (PEDOT:PSS) thin films with various electrical‐conductivity ranges are irradiated with gamma rays over a wide range of doses (1–50 kGy). Spectroscopic analyses reveal that the high‐energy irradiation results in changes in the doped state and chemical structure of the thin polymer films. Through the absorption measurement of the doped PEDOT:PSS films, the authors find that the films are relatively insensitive to irradiation and that the neutral state peaks in the de‐doped PEDOT decrease relative to the doped state as the gamma‐ray dose increases. The gamma‐ray irradiation up to 50 kGy results in a decrease in electrical conductivity in the already doped polymer films whereas it induces re‐doping and electrical‐conductivity enhancement in the chemically de‐doped ones. The high‐dose irradiation also induces chemical cross‐linking, resulting in thin films that are robust against solvent dipping.