In the present work, a series of solid biopolymer electrolytes (SBEs) from carboxymethyl cellulose (CMC) doped with ammonium fluoride (NH4F) (0 - 13 wt. %) was successfully prepared by solution cast technique. SBE sample containing 9 wt.% NH4F was found to exhibit the highest ionic conductivity of 2.68 x 10-7 Scm-1 at ambient temperature. XRD analysis revealed that the SBE samples containing NH4F salt to be semi-crystalline in nature. FTIR spectra showed that the interaction between CMC and NH4F has occurred in the polymer-salt system and the CMC-NH4F SBE system was a proton conductor.