Optical, thermal, crystalline, conductivity and dielectric properties of chlorinated polyethylene/poly (vinyl chloride) (CPE/PVC) blend composites with various loadings of copper alumina (Cu-Al$_2$O$_3$) nanoparticles were investigated in this work. The optical absorbance measured by UV–visible spectroscopy manifests the successful reinforcement of CPE/PVC blend by Cu-Al$_2$O$_3$ nanoparticles. The bandgap energies of nanocomposites were determined using Tauc’s equation and the minimum bandgap was obtained for 7 wt% loading. The X-ray diffractometer studies emphasized the enhanced crystallinity of nanocomposites relative to bare blend and the crystallinity increased with increasing filler concentration. The thermal properties of the samples were studied by thermogravimetric analysis and the results demonstrated a decrease in the rate of thermal degradation for nanocomposites compared to the polymer blend, revealing the excellent thermal stability of nanocomposites. AC conductivity studies were carried out at different temperatures and the conductivity of all the nanocomposites was improved compared to the CPE/PVC blend. The Coulomb barrier of charge carriers was determined using Coulomb barrier height model and the results showed a decrease in barrier height with an increase in temperature. The activation energy calculated from the Arrhenius plot decreases as a function offrequency. Temperature-dependent electrical impedance measurements also supported the enhanced conductivity at higher temperatures. The dielectric constant of CPE/PVC blend nanocomposites of various loadings of Cu-Al$_2$O$_3$ decreased with frequency and increased with temperature. The experimental values of dielectric constant were correlated with different theoretical models. The model based on Maxwell-Garnet equation was in good agreement with the experimental dielectric constants of the polymer nanocomposites.