In this study, a new type of packaging film assembled by caffeic acid-grafted-chitosan/polylactic acid (CA-g-CS/PLA) was prepared, and its characteristics, migration properties and effect on the postharvest quality of Agaricus bisporus, including physicochemical characteristics and antioxidant capacity, were analysed and evaluated. The results showed that compared to the traditional polyethylene (PE) film, the CA-g-CS/PLA film had a significantly improved water vapour transmission rate, oxygen transmission rate and migration properties (P < 0.05). Meanwhile, CA-g-CS/PLA could effectively delay the browning and respiration rate, and could form an O2/CO2 atmosphere to delay the ageing of Agaricus bisporus. Moreover, CA-g-CS/PLA effectively decreased the accumulation of malondialdehyde, superoxide radical and hydrogen peroxide content, and enhanced the activities of superoxide dismutase and catalase activity in mushroom during 15 d storage compared to PE. Therefore, the CA-g-CS/PLA film could be used as a novel active packaging material in the postharvest storage and transportation of Agaricus bisporus.