A chitosan film with acetylation degree close to 2% was crosslinked with glutaraldehyde. The consequences of this chemical modification were studied on the polymer gas and water transport properties. The crystalline domains were not affected by the crosslinking reaction and the modification of the amorphous phase did not induce variation of the gas permeability at anhydrous state. A crosslinking of 5 h, leading to a theoretical amine conversion of 60% in the amorphous phase induced only small changes of the polymer water sorption capacity at relative pressures less than 0.5. The main modification of the transport properties induced by this treatment occurred at a relative pressure equal to one with a significant reduction of the water sorption and water permeation and with the impossibility to measure the gas permeability coefficient in these conditions due to the brittleness of the membrane.