According to previous studies on moisture effect, it is stated that moisture enhances the electronic properties of polymeric materials. A theoretical study based on density functional theory calculations at B3LYP/3-21g* is performed for investigating the effect of moisture on sodium carboxymethyl cellulose (Na-CMC) as monomer, dimer, trimer and emeraldine base. Results indicated that due to moisture, TDM is increased while HOMO/LUMO band gap energy is decreased for the four proposed structures for Na-CMC. All results indicated that there is a change occurring in the electronic properties as a result of moisture. Furthermore, as a result of increasing the degree of polymerization, the total dipole moment (TDM) of Na-CMC is increased and equals 7.7141, 28.0388, 24.0199 and 38.3464 Debye for monomer Na-CMC, dimer Na-CMC, trimer Na-CMC and emeraldine base Na-CMC respectively. However, the highest occupied and the lowest unoccupied energy gap (HOMO/LUMO band gap energy) decreased and equals 0.9040, 0.3448, 0.1241 and 0.9021 eV for the same sequence. Additionally, the results of ESP study of all model molecules are in good agreement with the results of TDM and HOMO/LUMO band gap energy.