AbstractLow‐density polyethylene films, 80 μm thick, were exposed to microwave radiation and the following parameters were characterized: (i) the monoclinic to orthorhombic phase transformation, crystallinity and crystallite size using wide‐angle X‐ray diffraction, (ii) mechanical properties, and (iii) light absorption in the wavelength range of 200—800 nm. The following effects have been detected after microwave treatment: The major orthorhombic phase component increased, the monoclinic component decreased, the orthorhombic crystallite size decreased, the crystallinity, which was taken as the ratio of the scatter from the orthorhombic phase to the total scatter under the whole diffraction scan, increased. The mechanical properties improved. No change in the absorption of light was