The results of studies of 2.0–17.0 GHz frequency responses of S11 and S21 values of flexible electromagnetic radiation shields made of metallized polymer film, on the surface of which a coating of the Fe–Ni system is applied by electron beam evaporation, are presented. It has been experimentally established that an alloy in the Fe–Ni system containing 56 wt. % (~ 57 at. %) Fe and 44 wt. % (~ 43 at. %) Ni is azeotropic one. Such composition corresponds to the minimum temperature at which the total vapor pressure reaches 10 Pa. It has been determined that by applying of the Fe–Ni system coating with the specified content of components to the surface of a metallized polymer film, it is possible to reduce S11 value by a maximum of 5.0 dB and S21 value by a maximum of 6.7 dB in the frequency range of 2.0–17.0 GHz of this film.