Novel bio-based lightweight sandwich-structured composites with both skin and core materials made from biofiber and poly(lactic acid) (PLA) matrix were developed. The composites contained 48 wt% cellulose fiber and 52 wt% PLA matrix. The fabrication process was simple and required no adhesive for the skin-core bonding. The effects of fiber weight fraction and density on the core compressive properties were evaluated experimentally. Fifty percent of fibers gave the best results among the three fiber weight fractions studied and was used in preparing cores for subsequent fabrication of the sandwich-structured composites. The flexural properties and failure modes of the sandwich-structured composites were assessed. The flexural properties of the composites met the published deflection requirements for automotive load floor applications. Since these biocomposites were made using natural renewable materials that are fully biodegradable and recyclable, they show potential to be used as environmentally friendly alternatives to the existing products.