Biopolymer-based surgical sutures are commonly made from biopolyesters such as poly(glycolic acid) (PGA) and Polyglactin 910 (copolymer of lactic and glycolic acid). However, such materials have acidic degradation products. Another bio-based polymer, thermoplastic starch (TPS), is developed to tackle this problem. TPS has glucose as its main degradation product, however, it has poor mechanical properties. To tackle this problem, a reinforcement material is added. In this research, TPS is synthesized from sago (Metroxylon sagu) starch plasticized with two types of plasticizer (glycerol and sorbitol, 30% wt.) and reinforced with microcrystalline cellulose (MCC) at various concentrations (0%, 2%, 5%, and 10% wt.). Specimens were subjected to a tensile test (ASTM D 638) to obtain the values of strain at break, tensile strength, and Young's modulus. Results show that tensile strength peaks at 2% MCC concentration, while elongation at break generally decreases with the addition of MCC. The value of Young's Modulus increases with the addition of MCC for the glycerol-plasticized specimens, while no significant trends are observed among the sorbitol-plasticized specimens. The addition of 2% MCC into sorbitol-plasticized sago starch results in an improvement in tensile strength to 4.68 MPa and Young's Modulus to 45.01 MPa. Such a sample has the highest tensile strength and Young's Modulus out of all specimens, thus being the most feasible for surgical suture material. © 2025 Author(s).