Water-insoluble curcumin was found to be well dissolved in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl), which is also an effective solvent for cellulose. Using AmimCl as the solvent, cellulose/curcumin composite films with various curcumin contents ranging from 0 to 5 wt% were prepared by solution-mixing and casting. The obtained films containing curcumin were highly transparent with a bright yellow color. These composite films possessed good mechanical properties and thermal stability, both of which are comparable to the pure cellulose films. The SEM observation of the fracture surface of the cellulose/curcumin composite films indicated the uniform distribution of curcumin in the matrix. The antibacterial activity of the composite films was examined by a zone method against E. coli. The results showed that the cellulose/curcumin composite films exhibited obvious antibacterial activity, and the inhibition zone diameter against the bacterium was proportional to the curcumin content in the composite films. Hence, these cellulose/curcumin composite films prepared entirely from natural resources can be considered as novel kinds of functional films and could find applications in food packaging and medical fields. © 2012 The Royal Society of Chemistry.