There is demand for application of polymer materials in electrochemical devices, especially natural polymers, because of their superiority in mechanical integrity, affordability and biodegradability. In this work, solid biopolymer electrolyte (SBEs) comprising 2-hydroxyethyl cellulose (2-HEC) doped with different weight percentage of ammonium thiocyanate, NH4 SCN (0 – 44 wt.%) were prepared using a facile solution casting technique. The effects of NH4 SCN on ionic conductivity and dielectric properties of SBEs were investigated using electrochemical impedance spectroscopy (EIS). The ionic conductivity recorded at room temperature showed massive improvement for pure 2-HEC from the value of 5.93 x 10-8 S cm-1 to 1.16 ×10-4 S cm-1, comprising 36 wt.% NH4 SCN. Meanwhile, at elevated temperatures, the ionic conductivity revealed the Arrhenius behaviour, where it increased proportional to the temperatures. In addition, by introducing NH4 SCN content as a proton donor, it also effectively reduced the activation energy of the SBEs, which further support enhancing the ionic conductivity. In dielectric permittivity study, the εr and εi increased as the NH4 SCN content increased, revealing the non-Debye dependency of the SBEs, which indicates that the SBEs are ionic conductors. The addition of the optimum value of NH4 SCN content showed good characteristic for electrochemical devices applications.