Abstract: To address the needs for moisture control, antimicrobial activity, and quality preservation during postharvest storage of button mushrooms, this study developed a bio-based packaging material with sustained release ability and structural stability. Chitosan (CS) and bacterial cellulose (BC) were used as the film-forming matrix. Cinnamaldehyde (CA) was loaded into MIL-101(Fe) to prepare a CA loaded controlled-release assembly. This assembly was further introduced into the chitosan/bacterial cellulose composite system to prepare an active composite film. CS has good film forming ability and natural antibacterial activity. However, it also has some limitations, such as high hydrophilicity and poor water resistance. BC has high crystallinity and good mechanical properties, and it can provide structural support for the film. CA has strong antibacterial activity, but it is highly volatile and has limited stability. Loading CA into MIL-101(Fe) may improve its stability and allow sustained release. This may further improve its performance in active food packaging. The encapsulation efficiency and loading capacity of the CA-loaded material were determined. Its release behavior under different temperatures, food simulants, and pH conditions was also evaluated. Subsequently, the composite films were prepared by the casting method. Single-factor experiments were first carried out to investigate the effects of CS content, BC content, glycerol content, and CA@MIL-101(Fe) content on the properties of the composite films. Based on these results, the formulation was further optimized by orthogonal experiments. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterize the changes in functional groups, surface microstructure, and crystal structure of the composite films. The antibacterial activity of the films against Escherichia coli, Staphylococcus aureus, and Pseudomonas tolaasii was further evaluated by the inhibition zone method. In addition, low temperature storage tests were carried out to analyze their effects on weight loss, hardness, whiteness, browning index (BI), electrical conductivity, malondialdehyde (MAD) content, and polyphenol oxidase (PPO) activity of Agaricus bisporus. The results showed that the loading capacity and encapsulation efficiency of CA in MIL-101(Fe) were 49.99% and 74.3%, respectively. This indicates that the carrier had a good capacity for loading active compounds. The release of CA showed a biphasic pattern, with a fast release at the early stage and a slow release at the later stage. The release behavior was also clearly affected by food simulants and pH conditions. After formulation optimization, the optimal active composite film was obtained. It was prepared with a chitosan concentration of 0.016 g/mL, a BC concentration of 0.005 g/mL, a glycerol content of 20%, and a CA@MIL-101(Fe) concentration of 0.004 g/mL. The tensile strength (TS), elongation at break (EAB), moisture absorption (M_A), and water vapor permeability (W_vp) of the film were 25.79 MPa, 22.77%, 254.69%, and 6.347 × 10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹, respectively. These results indicate that the film achieved a good balance among mechanical properties, moisture control ability, and packaging suitability. Antibacterial tests showed that the composite film loaded with active components exhibited strong inhibitory effects against all three tested bacteria. Its antibacterial activity was clearly better than that of the control film without active components. Storage tests showed that the active composite film significantly reduced weight loss, BI, electrical conductivity, and MAD content of Agaricus bisporus during cold storage. It also inhibited the increase in PPO activity and maintained relatively high hardness and whiteness. These results indicate that the film could effectively delay postharvest water loss, membrane lipid peroxidation, enzymatic browning, and tissue softening of Agaricus bisporus. The CA@MIL-101(Fe)/CS/BC active composite film developed in this study showed good structural stability, sustained release activity, and preservation function. It improved the packaging microenvironment and continuously released CA. These effects worked together to delay quality deterioration of Agaricus bisporus. The film shows good application potential. It can provide theoretical support and technical reference for the design and development of active packaging materials for edible fungi and other high-moisture agricultural products.