Hybrid films have been obtained by crazing high-density polyethylene (HDPE) in a poly(ethylene oxide) (PEO) solution. Deformation by the crazing mechanism gives rise to the formation of a nanoporous structure in HDPE, with the PEO solution penetrating into it. A uniform HDPE-PEO hybrid film is obtained after the solvent is removed. The structure of crazed HDPE has been shown to govern the structure of incorporated PEO. By wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR), we have found out, that PEO crystallization in HDPE film is accompanied by an orientation and a decrease in the crystallinity and melting temperature of PEO due to the spatial confinements caused by the nanoporous HDPE matrix. The revealed effects depend oh the pore size, which is, in turn, determined by the degree of HDPE deformation (tensile strain). The lower the strain (HDPE pore size), the greater the decrease in the crystallinity of incorporated PEO. As the tensile strain of HDPE is increased, the orientation of PEO lamellae in the HDPE film changes and flat-on lamellae of PEO arise in addition to edge-on lamellae.