Composites were prepared by mixing thermoplastic biodegradable polymers with sea algae fibers. Tensile mechanical properties were analyzed as a function of fiber concentration. The effect of processing, such as compression molding and calendering, on the mechanical properties of the materials was investigated. Composites showed higher elastic modulus and lower strength than the matrix components. Fiber damaging, characterized by a reduction of both length and diameter, was observed in the composites. Films, prepared by calendering operations, showed anisotropic properties due to fiber alignment.