Poly(3-hydroxybutyrate) (PHB) films and its nanocomposites were obtained by casting. Three types of modified clays were used in order to improve the compatibility with the PHB. The films were characterized determining the thermal properties and the non-isothermal crystallization kinetic parameters from the melt. No change in the melting temperature of PHB was observed with the clay addition but the T-g diminished for the nanocomposites with the clay modified by ion exchange (MI) and by acid activation (MAI) to the PHB, due to the effect of the organic modifiers. From non-isothermal studies, it was observed a diminution of the peak of the crystallization temperature of PHB with the addition of clay at all of the cooling rates studied. The nanocomposites with MI and MAI exhibited the slowest crystallization rate among the materials, studied by the Liu-Mo model. However, the addition of the clay modified by silylation (MAGI) did not affect the crystallization rate of PHB. Effective activation energy (E alpha) of the crystallization process of PHB and the nanocomposites was calculated by the isoconversional methods of Friedman and Vyazovkin. The E alpha of the PHB increased with the addition of any type of the clays studied, but the rate of crystallization was reduced. (C) 2014 Elsevier B.V. All rights reserved.