The thermoplastic starch (TPS)/cellulose biocomposites were manufactured as green biocomposite films. TPS was produced through plasticization process in which the mixture of starch granule and plasticizers (water and glycerine) went through the stirring and heating process. Cellulose was used as filler and prepared in suspension form through ultrasonication process involving isolation of cellulose in water medium. The ultrasonicated cellulose suspension was added into the TPS matrix to produce TPS/cellulose biocomposites by film casting. The effects of ultrasonication duration (1, 2, 3, 4 and 5 hours) on the crystallinity and tear strength of the TPS/cellulose biocomposite films were investigated. Based on the XRD results, crystallinity of the cellulose and biocomposite were altered by the cellulose ultrasonication process. The tear strength of the TPS biocomposites were greatly enhanced when 5-hours ultrasonicated cellulose was employed as filler. The biocomposites demonstrated 241% higher tear strength than the pure TPS film. This could be related to the transformation of the cellulose into more isolated fiber, with enhanced crystallinity for better reinforcing effect to the TPS matrix.