Nanocomposite polymer electrolytes (NCPE), with varying concentrations of Al2O3 nanofiller in an optimized composition containing 75:25 wt% ratio of poly-epsilon-caprolactone (PCL) and zinc trifluoromethanesulfonate (ZnTr), were prepared by solution casting method. A maximum ionic conductivity of 2.5 x 10(-5) S cm(-1) was achieved at room temperature for 5 wt% loading of the nanofiller. Crystalline peaks observed in the X-ray diffraction pattern were deconvoluted from the amorphous halo to estimate the degree of crystallinity of the prepared NCPEs. Scanning electron microscopic evaluation indicated the reduction in the spherulite size of NCPE with the incorporation of nanofiller. Cationic transference number () of the typical NCPE with 5 wt% nanofiller was found to be > 0.5, whereas the decomposition voltage of the polymer electrolyte increased from 2.5 to 2.7 V with the incorporation of the Al2O3 nanofiller. The prepared NCPE could be used to fabricate eco-friendly primary as well as secondary battery systems.