Due to the rapidly increasing biological applications and antibacterial properties of versatile nano cerium oxide particles, the effects of these particles on chitosan-based films were investigated. Chitosan-based composite films with and without cerium oxide nanoparticles (NPs) were prepared by a casting method. Hydroxyethylcellulose (HEC) was used for the flexibility of films, and polyethylene glycol (PEG) was used as a plasticizer in the blending stage of film preparation. Characterizations of films were done by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). Cerium oxide nanoparticle incorporation enhanced the antibacterial activity of chitosan-based films against Escherichia coli and Staphylococcus aureus. This composite film is proposed as packaging or coating material because of its flexibility, antibacterial efficacy, and good mechanical strength. ? 2021 Elsevier B.V. All rights reserved.