Broadband Dielectric Relaxation Spectroscopy was performed to study the molecular dynamics of dried Bacterial Cellulose/Carboxymethyl Cellulose-Graphene Oxide (BC/CMC-GO) composites as a function of the concentration of CMC in the culture media. At low temperature the dielectric spectra are dominated by a dipolar process labelled as a β-relaxation, whereas electrode polarization and the contribution of dc-conductivity dominate the spectra at high temperatures and low frequency. The CMC concentration affects the morphological structure of cellulose and subsequently alters its physical properties. X-ray diffractometry measurements show that increasing the concentration of CMC promotes a decrease of the Iα/Iβ ratio. This structural change in BC, that involves a variation in inter- and intramolecular interactions (hydrogen-bonding interactions), affects steeply their molecular dynamics. So, an increase of CMC concentration produces a significantly decrease of the β-relaxation strength and an increase of the dc-conductivity. © 2016 Elsevier Ltd