Polymer electrolytes comprising a blend of poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA) with different concentrations of LiBF4 are prepared using a solvent-casting technique. The structure and complexation of the electrolytes are studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The ionic conductivities of the electrolytes are measured in the temperature range 302–373K. The maximum conductivity (1.2886×10−3 Scm−1) is obtained for a polymer complex with 8wt.% LiBF4. The thermal stability of this electrolyte is examined by thermogravimetric/differential thermal analysis (TG/DTA).