In this study, gallic acid grafted chitosan (GA-g-CS) film was used as a novel active packaging material for the preservation of Agaricus bisporus . Effect of GA-g-CS film packaging on the physico-chemical parameters and enzyme activities of A. bisporus during cold storage was investigated. As compared to mushrooms packaged with chitosan (CS) film and commercially used polyethylene (PE) film, mushrooms packaged with GA-g-CS film showed significantly lower respiration rate, browning degree, malondialdehyde content, electrolyte leakage rate, superoxide anion production rate and hydrogen peroxide content. Among all the treatment groups, mushrooms packaged with GA-g-CS film exhibited the highest superoxide dismutase and catalase activities as well as total phenolic content, however, the lowest polyphenol oxidase activity. Our results suggested GA-g-CS film packaging could increase the antioxidant status of A. bisporus , which in turn maintained the postharvest quality of mushrooms.