Polylactic acid (PLA)-based nanocomposite films, containing up to 5% by weight of two types of nanoclays: sepiolite needle-like clay and halloysite nanotube clay, were prepared via industrially viable melt processing route. Clays modify the crystallinity of the hosting PLA affecting its gas barrier and mechanical properties. Annealing treatments of composite films were found to be critical in the optimization of these properties with an additional enhancement in crystallinity and stiffness especially in presence of clays. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39798.