PEO/B 4 C nanocomposite films with various concentrations of B 4 C-NPs are fabricated by the casting method. The chemical and crystal structure, thermal, optical, electrical, and morphological properties of PEO/B 4 C nanocomposites films are examined. The PEO/B 4 C nanocomposite films have semicrystalline nature, and the amorphous phase is dominant in all PEO/B 4 C nanocomposite nature. Moreover, the crystallinity degree and the melting enthalpy ( Δ H m ) decrease as revealed by the XRD and DSC analysis, and the crystallinity behavior is the same, whether deduced from XRD or DSC. The slight shifting in the vibrational bands upon introducing B 4 C-NPs into PEO films confirms the formation of the charge transfer between the two materials. Furthermore, the transmittance ( T ) spectra, refractive index, and packing density values exhibited a substantial reduction due to adding different concentrations of B 4 C-NPs into the PEO films. Further, the conductivity value of PEO/B 4 C nanocomposite increases due to the increase in B 4 C-NPs contents in PEO nanocomposite. The SEM micrographs revealed that the pure PEO film has a very smooth surface with tiny cracks compared to others. The PEO/B 4 C nanocomposite films with B 4 C-NPs are composed of nanoparticles within the polymer matrix, accumulative nanoparticles on the surface, and cracks. These PEO/B 4 C nanocomposite films may be employed as an anti-corrosion coating.