This review comprehensively analyzes bacterial cellulose-based composites for electromagnetic interference shielding applications, focusing on the composites’ mechanical, thermal, electrical, and Joule heating properties. With the increasing use of electronic devices, effective EMI shielding materials are crucial to mitigate electromagnetic radiation that can disrupt device functionality. BC, as a natural biopolymer, offers sustainability, excellent mechanical strength, and thermal stability but requires modification with conductive materials such as MXene (Ti3C2Tx), silver nanowires (Ag NWs), and graphene nanosheets (GNs) to improve its dielectric properties. A systematic review of 26 composites revealed that material composition, thickness, and processing methods critically influence EMI shielding effectiveness (SE). For example, composites like BC/Ag, with a thickness of 0.0012 mm, achieved the highest SE of 53 dB, while Ti₃C₂Tx-enhanced composites like Ti3C2Tx/LM/BC and BC@Fe3O4/CNT/Ti3C2Tx reached 61.84 dB and 71.3 dB, respectively. Mechanical properties, such as tensile strength and Young’s modulus, are optimized through careful material composition, with MXene/BC/APP exhibiting a tensile strength of 131.5 MPa. The review also highlights the importance of thermal conductivity, with BC/GNP reaching 80.2 W·m⁻1·K⁻1, and Joule heating performance, where CNF@BNNS/AgNW/BC achieved 196 °C in 8 s. The findings underscore the potential of BC-based composites as efficient, lightweight, and environmentally friendly materials for EMI shielding. Future research directions include optimizing material combinations, improving structural designs, and refining processing techniques to enhance the multifunctionality of these composites.