The addition of CMC to starch-glycerol blends improved the moisture resistance of the resulted starch based composites. At the level of 15%W/W CMC, blend films showed the lowest WVP values at 2.34×10−7 g/m.h.Pa. However when the CMC content of the blend films reached to 20% W/W starch, the WVP increased to 2.38×10−7 g/ m.h.Pa. By addition of 15%W/W CMC/starch, the moisture absorption and solubility of the films decreased from 24.34% and 23.76% to 20.00% and 19.89%, respectively. Furthermore, CMC had an important influence on the mechanical properties of the resulted composite films. CMC (20% W/W starch) could increase the UTS of starch based composite films by more than 59% compared to the neat plasticized starch film.