A mixture of corn starch and glycerol plasticizer (CSG) was blended with latex natural rubber (LNR) and carboxymethyl cellulose (CMC). The addition of 10 phr of CMC improved the Young’s modulus (6.7 MPa), tensile strength (8 MPa), and elongation at break (80%) of the CSG/LNR blend. The morphology of the CSG/LNR/CMC blends showed a uniform distribution of LNR particles (1-3 µm) in the CSG matrix. The addition of CMC enhanced the swelling ability and water droplet contact angle of the blends owing to the swelling properties, interfacial crosslinking, and amphiphilic structure of CMC. Fourier transform infrared spectroscopy confirmed the reaction between the C=C bond of LNR and the carboxyl groups (-COO-) of CMC, in which the Na+ ions in CMC acted as a catalyst. Notably, the mechanical properties of the CSG/LNR/CMC blend were improved owing to the miscibility of CSG/CMC and the CMC/LNR interfacial reaction. The CSG/LNR/CMC biodegradable polymer with high mechanical properties and interfacial tension can be used for packaging, agriculture, and medical applications.