Biopolymer electrolyte based on carboxymethyl cellulose has been prepared by doping with different concentration of oleic acid via solution casting technique. Fourier Transform Infrared spectroscopy was used to study the complexation between the salt and polymer. New peak was observed at 1710, 2850, 2920 cm^-1. X-ray diffraction study reveals the amorphous nature of the biopolymer electrolyte. Impedance study shows the highest ionic conductivity, σ, was found to be 2.11 × 10^-5 S·cm^-1 at room temperature (303 K) for sample containing 20 wt.% of oleic acid and the biopolymer electrolyte obeys Arrhenius behaviour.