A simple open-mill mixing approach was employed to develop thermally and mechanically stable nanocomposites consisting of poly (ethylene- co-vinyl acetate) (EVA) as the matrix and boron nitride (BN) as a reinforcing nanofiller. The development of nanocomposites was examined by FT-IR, UV spectroscopy, XRD, TEM, TGA and DSC. The attachment of BN to EVA was confirmed by the characteristic BN band at 602 cm−1 in the FT-IR spectra. The UV measurements revealed a red shift in the nanocomposites due to nanoparticle interactions with polymer chains and the bandgap energy decreased with the nanofiller concentration. The XRD TEM analysis indicated the presence of a crystalline BN phase in EVA. Enhanced thermal stability and glass transition temperature of the polymer with the addition of BN nanoparticles were revealed from TGA and DSC, respectively. The EVA with 5% BN nanocomposite was discovered to have higher mechanical properties, electrical conductivity and lower optical bandgap energy. The tensile strength, tear resistance, impact strength and hardness of EVA increased with the inclusion of BN, whereas elongation at break was reduced. The findings of the experiments showed that the EVA/BN nanocomposites would provide excellent options for mechanically and thermally stable materials for energy storage applications.