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Heat accumulation generated from confined space poses a threat to the service reliability and lifetime of electronic devices. To quickly remove the excess heat from the hot spot, it is highly desirable to enhance the heat dissipation in a specific direction. Herein, we report a facile route to fabricate the large-scale composite film with enhanced thermal conductivity and electrical insulation. The well-stacked composite films were constructed by the assembly of polydopamine (PDA)-modified graphene nanosheets (GNS_PDA) and hexagonal boron nitride (BN_PDA), as well as bacterial cellulose (BC). The introduction of the PDA layer greatly improves the interface compatibility between hybrid fillers and BC matrix, and the presence of GNS_PDA-bridging significantly increases the probability of effective contact with BN_PDA fillers, which is beneficial to form a denser and complete “BN-GNS-BN” heat conduction pathway and tight filler–matrix network, as supported by the Foygel model fitting and numerical simulation. The resulting BC/BN_PDA/GNS_PDA film shows the thermal conductivity and tensile strength of 34.9 W·m⁻¹·K⁻¹ and 30.9 MPa, which separately increases to 161% and 155% relative to the BC/BN_PDA film. It was found that the low electrically conductive and high thermal conductive properties can be well balanced by tuning the mass ratio of GNS_PDA at 5 wt%, and the electrical conductivity caused by GNS_PDA can be effectively blocked by the BN_PDA filler network, giving the low electrical conductivity of 1.8 × 10⁻¹⁰ S·cm⁻¹. Meanwhile, the BC/BN_PDA/GNS_PDA composite films effectively transfer the heat and diminish the hot-spot temperature in cooling LED chip module application. Thus, the present study may pave the way to promoting the industrialization of scalable thermal management devices.