Alginate-based nanocomposites at different montmorillonite clay (MMT) loadings were produced by solvent casting method. The combined effect of biopolymer and MMT content on the mechanical and physical properties of the obtained nanocomposites was investigated. The MMT weight percent relative to alginate was varied from 1% to 5% and polymer concentration was 1 and 1.5% w/v. Films containing 5% (wt/wt) of MMT show, with respect to neat alginate, reduced water permeability of about 19% and 22% and an increased water solubility of about 36% and 40%, for 1% and 1.5% alginate films, respectively. The tensile strength of neat alginate films increased significantly with increasing alginate concentration (about 36%) but slightly increased with increasing clay content up to 3%. The values of elongation decreased with increasing the both of clay content and polymer concentration. Results on X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed well developed exfoliated nanocomposite films especially at low level of nanoclay addition. (c) 2013 Elsevier Ltd. All rights reserved.