The mechanical, thermal, and morphological properties of polycaprolactone (PCL) and green coconut fiber (GCF) composites were evaluated. Blends containing acrylic acid-grafted PCL (PCL-g-AA/GCF) exhibited noticeably better mechanical properties due to better compatibility between the two components. The dispersion of GCF in the PCL-g-AA matrix was significantly more homogeneous due to the creation of branched and cross-linked macromolecules via reactions between carboxyl groups in PCL-g-AA and hydroxyl groups in GCF. The tensile strength of the PCL-g-AA/GCF composites at break was considerably greater than that of PCL/GCF composites. In addition, the PCL-g-AA/GCF blend was more easily processed due to lower melt viscosity. Biodegradation tests were performed with each composite in an Acinetobacter baumannii BCRC 15556 environment. The mass of both composites was reduced by the GCF content within 4 weeks. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 948-956, 2010