Biodegradable chitosan/clay nanocomposite membranes were prepared by solution casting method for the application of dehumidification. The cationic biopolymer, chitosan was intercalated into clay through cationic exchange and hydrogen bonding process. Diluted acetic acid was used as a solvent for dissolving and dispersing chitosan into clays. Chitosan was successfully intercalated into clay and it was confirmed by X-ray diffraction method. Thermal stability and the mechanical properties of the nanocomposites are characterized by TGA and Universal Testing Machine. Thermal stability and mechanical properties were enhanced by increasing clay contents in chitosan/clay nanocomposites. Gas permeation and water vapor permeation properties of the nanocomposites were measured by time-lag methods. Permeability of N2 gas and water vapor through chitosan/clay nanocomposite membranes decreased when the content of clay in the nanocomposite increased.