Chitosan (CS), a bio-renewable natural material, has the potential to be utilized as a biopolymer for food packaging films (PFs)/coatings. However, its low solubility in dilute acid solutions and poor antioxidant and antimicrobial activities limit its application in PFs/coatings. To address these restrictions, chemical modification of CS has garnered increasing interest, with graft copolymerization being the most extensively used method. Phenolic acids (PAs) as natural small molecules are used as excellent candidates for CS grafting. This work focuses on the progress of CS grafted PA (CS-g-PA) based films, introducing the chemistry and methods of preparing CS-g-PA, particularly the effects of different PAs grafting on the properties of CS films. In addition, this work discusses the application of different CS-g-PA functionalized PFs/coatings for food preservation. It is concluded that the food preservation capability of CS-based films/coatings can be improved by modifying the properties of CS-based films through PA grafting.