Abstract The structural characteristics and mechanical properties of coir fiber/polyester composites were evaluated. The coir fibers were obtained from disregarded coconut shells that if not properly processed constitute an environmental hazard. The as-received coir fiber was characterized by scanning electron microscopy coupled with X-ray dispersion analysis. Composites prepared with two molding pressures and with amounts of coir fiber up to 80 wt% were fabricated. Up to 50 wt% of fiber, rigid composites were obtained. For amounts of fiber higher than this figure, the composites performed like more flexible agglomerates. The results obtained for flexural strength allowed comparison of the technical performance of the composites with other conventional materials.