As the demand for sustainable and environmentally friendly materials has increased, renewable resources have been explored for the development of biobased composites. Two biobased composite materials were developed from thermoplastic starch (TPS), short fibers from plantain pseudostems sheaths and the starch from the plantain pseudostem core, using twin-screw extrusion and compression molding. Based on the findings, there is evidence of a biobased composite material with reduced water absorption of up to 9.9%, keeping thermal stability at a degradation temperature between 300 and 306 °C and increasing tensile properties by over 506%, although hardness showed slight increases (4.6%). In addition, the capacity of the sheath to generate a water vapor barrier is highlighted by reducing the magnitude of losses in mechanical properties during storage for a period of 8 days. This study contributes to the use of agricultural residues to create sustainable products, offering a pathway toward reducing dependency on synthetic polymers and mitigating environmental impact.