Edible biopolymer-based coatings are gaining attention as sustainable alternatives to synthetic fungicides for postharvest preservation, yet their practical application is often constrained by formulation instability and limited antifungal efficacy. This study developed a novel rice bran wax–chitosan–deep eutectic solvent (ChiBran-DES) emulsion coating for controlling postharvest disease in fig (Ficus carica L.) fruit. The formulation combines the hydrophobic barrier properties of rice bran wax, the antimicrobial and film-forming capabilities of chitosan, and the multifunctional plasticizing and bioactive roles of deep eutectic solvent. Emulsion stability was evaluated over four weeks through visual phase separation, creaming index, sedimentation behavior, and refractive index analysis. The optimized formulation (ChiBran-DES1.5%) exhibited superior physicochemical stability, with improved zeta potential, reduced droplet size distribution, and enhanced structural uniformity, indicating strong interfacial interactions. The antifungal performance of ChiBran-DES1.5% was assessed against Colletotrichum gloeosporioides and compared with ChiBran and a commercial fungicide (anthracole). The coating demonstrated significantly enhanced antifungal activity, attributed to synergistic interactions between chitosan’s polycationic mechanism, the moisture barrier effect of rice bran wax, and the bioactivity of menthol–thymol DES. In vivo application on inoculated fig fruits further confirmed a substantial reduction in anthracnose incidence and disease progression during storage. Overall, the ChiBran-DES system presents a stable, biodegradable, and high-performance coating with strong potential to reduce reliance on synthetic fungicides in postharvest management.