Composite polymer electrolytes comprising of polyvinyl chloride (PVC), poly(butyl methacrylate) (PBMA), lithium perchlorate (LiClO4), ethylene carbonate (EC) and with different ratios of aluminium oxide (Al2O3) are prepared by solution casting technique and characterized. Structural and complex formations are confirmed from XRD and FTIR studies. Conductivity studies were carried out and found that as the Al2O3 concentration increases the conductivity is found to increase initially and then decrease after certain concentration. The room temperature ionic conductivity of polymer electrolyte film bereft of Al2O3 is found to be 0.116 mS cm−1 which increases to 0.712 mS cm−1 in electrolyte membranes with 10 wt% of Al2O3. Dielectric behaviour (ε′ and ε″) for the composite polymer electrolytes was found to decreases with increase in frequency due to existence of electrode polarization effect. The high dielectric constant and low dielectric modulus are observed for 10 wt% of Al2O3 incorporated PVC–PBMA composite polymer electrolyte compared to other Al2O3 concentrations. The morphology of polymer electrolyte membranes were studied by scanning electron microscope. © 2016, Springer Science+Business Media New York.