The understanding of the processing-morphology-property relationships of biopolymer/montmorillonite composites is essential for food packaging applications. This study presents the effects of the acetic acid and glycerol concentrations on the barrier properties of films of chitosan, glycerol, and organically modified montmorillonite (OM-MMT). In addition, their morphology and mechanical behavior were study. The plasticized chitosan composite films (5%wt OM-MMT) were made via solvent cast method, with acetic acid as solvent, and glycerol as plasticizer. Solutions having three different acid contents (1%v/v, 2%v/v, 4%v/v) and two plasticizer contents (15%wt, 30%wt) were evaluated trying to increase the amount of favorable intermolecular interactions with OM-MMT. The oxygen barrier properties, mechanical behavior, intercalation and morphology of the composite films were study by oxygen transmission rate (OTR), dynamic mechanical analysis (DMA), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The TEM, XRD and FTIR spectrums showed nanocomposites having a combination of intercalated and exfoliated morphologies. The composite with the lower acid content show a higher interplanar distance (d-001). Also, the oxygen barrier property improves with lower acid content, while the changes in mechanical properties with the different acid contents were not significant. These results are relevant because they show that the excess of acid in the solution hinder the exfoliation process of the OM-MMT during the mixing. However, the polar groups from the plasticizer facilitate the exfoliation process and in consequence promote an improvement on the oxygen barrier property.