Novel silk fibroin fiber reinforced poly(butylene succinate) (PBS) biocomposites have been developed by twin-screw extrusion and injection molding processes, varying the fiber content from 10 to 40 % by weight. The thermal stability, thermal expansion, dynamic mechanical, tensile, flexural, and impact properties and water absorption behavior of the biocomposites with various silk fiber contents are investigated. The obtained results are consistent with each other. The thermal stability of the biocomposites depends on the silk fibroin fiber content, reflecting the thermal characteristics of both PBS and silk fiber. The coefficient of thermal expansion is somewhat decreased by incorporating silk fibroin fibers into the PBS. The storage modulus, the tensile modulus, and the flexural properties are gradually increased with increasing the fiber content up to 40 wt%. The Izod impact strength is the highest at 20-25 wt% fiber content, as similarly found in the tensile strength. The percentage of water absorption is gradually increased with increasing the fiber content as well as the water immersion time.