The biodegradability, morphology, and mechanical properties of composite materials made of poly( butylene succinate adipate) (PBSA) and sugarcane bagasse (SCB) were evaluated. Composites containing maleic anhydride (MA)-grafted PBSA (PBSA-g-MA/SCB) exhibited noticeably superior mechanical properties because of greater compatibility between the two components. The dispersion of SCB in the PBSA-g-MA matrix was highly homogeneous as a result of ester formation between the carboxyl groups of PBSA-g-MA and hydroxyl groups in SCB and the consequent creation of branched and crosslinked macromolecules. Each composite was subjected to biodegradation tests in a Rhizopus oryzae compost. Morphological observations indicated severe disruption of film structure after 60 days of incubation, and both the PBSA and the PBSA-g-MA/SCB composite films were eventually completely degraded. The PBSA-g-MA/SCB films were more biodegradable than those made of PBSA and exhibited a higher intrinsic viscosity, implying a strong connection between these characteristics and biodegradability. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 427-435, 2011