In this work, solid biopolymer electrolytes (SBE) containing carboxymethyl cellulose (CMC) doped with ammonium thiocyanate (NH4SCN) were prepared via solution casting method. The ionic conductivity and dielectric properties of CMC-NH4SCN system were investigated by electrical impedance spectroscopy in the temperature range of 303-353 K. The dc conductivity shows that the highest ionic conductivity of 6.48 x 10-5 Scm-1 at ambient temperature was obtained when 25 wt.% of NH4SCN was incorporated. The temperature dependence of ionic conductivity revealed that CMC-NH4SCN system was discovered to obey Arrhenius law where the regression value is almost unity (R2?1). Activation energy of CMC-NH4SCN system was found to decrease with the increment of NH4SCN concentration. The dielectric behaviour of the CMC-NH4SCN system have been analyzed using dielectric permittivity (?*) and electrical modulus (M*) spectra. Results from dielectric studies showed a non-Debye behaviour of CMC-NH4SCN system