The combination of polyvinyl alcohol (PVA)/thermoplastic starch (TPS) as matrix resulted in the creation of PVA/TPS materials through rosin, which successfully substituted a part of glycerol and combined with cellulose nanocrystals (CNC). The mechanical properties of PVA/TPS materials were studied in relation to rosin and CNC, and the findings indicate a substantial rise in the crystallinity of the PVA/TPS composite system with rosin from 21.2% to 27.5%. The addition of both rosin and CNC to PVA/TPS through rotational rheometry enhances the viscosity of the composite system, and FT-IR results verify that rosin and PVA/TPS materials can be esterified, while CNC and PVA/TPS materials generate hydrogen bonds. SEM images demonstrate that the incorporation of rosin and CNC is successful in encouraging a more uniform distribution of PVA/TPS, and the tensile strengths of the PVA/TPS/rosin and PVA/TPS/rosin/CNC systems are augmented by 20% and 22%, respectively, in comparison to that of PVA/TPS.