Abstract This research was conducted to synthesize biodegradable plastic films from chitosan and glycerol with the addition of cellulose nanowhiskers as a reinforcing agent. Cellulose synthesis of nanowhiskers from coconut husks was carried out with 3 phases, i.e., pre-treatment, bleaching, and sulphuric acid hydrolysis with a concentration of 55%. The result of cellulose hydrolysis in the form of needle-like nanowhiskers with an average of 223.6 nm particle size and a crystallinity index of 34.27% were shown through the results of FTIR, SEM, PSA, and XRD. Plastic film was made by blending method, which was mixing whole material then stirred until homogeneous and printed at room temperature. This study showed that the addition of cellulose nanowhiskers 3% can increase the tensile strength value up to 50 MpA, water resistance by 88.86%, and the biodegradation rate by 0.51 mg/day, but the value decreased if the addition of cellulose nanowhiskers was more than 3%. This was influenced by the rigid properties of cellulose nanowhiskers and experienced aggregation if it was added in excess. In conclusion, the addition of cellulose nanowhiskers with precise concentration can increase the tensile strength, water resistance, and the rate of biodegradation in the plastic film from chitosan-glycerol.