A novel biocomposites double-layer films using polyhydroxybutyrate (PHB) and cellulose paper were produced. The biocomposites were prepared by the solvent-casting method (with chloroform). Films of the blends were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron micrograph (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray (XR) and surface roughness measurements. Moisture absorption, water absorption and water vapor permeation. of films has been investigated. The PHB impregnated the fibers of cellulose paper and it was on the valley of paper structure. The double-layer films showed diminutions in the moisture absorption, in the water abortion, in water vapor permeation and in surface roughness. According to contact angle, surface free energies and the barrier properties of the films can be considered more hydrophobic. The experimentally observed tensile properties (modulus and tensile strength) of double-layer films with different content of PHB were determined. Measurements show the tensile strength and modulus of cellulose paper increases with the percentage of PHB. SEM photomicrographs of the fractured films surfaces were also analyzed. It was possible to obtain a biodegradable material with little amount of PHB to improve the barrier and the mechanical properties of cellulose paper, taking advantage of the good properties of both materials. (c) 2007 Wiley Periodicals, Inc.