Abstract: Two-dimensional hexagonal BNNS are promising electrically insulating and thermally conductive materials for high-frequency electronics, high-power devices, and new energy storage systems, owing to their high in-plane thermal conductivity, high breakdown strength, wide bandgap, and low dielectric constant. However, pristine BNNS suffers from strong surface chemical inertness, severe sheet restacking, and poor interfacial compatibility with organic matrices. Conventional polar-group modification often degrades dielectric properties. Fluorination introduces B−F bonds on BNNS to tune the interfacial electronic structure, improve sheet dispersion and interfacial adhesion, and suppress carrier transport, thereby achieving a synergy of thermal conduction, dielectric, and insulating performances. This review summarizes two categories of preparation routes for fluorinated boron nitride nanosheets: top-down and bottom-up strategies. The fluorination uniformity, structural integrity, and scale-up feasibility of different methods are compared. The modulation mechanisms of fluorination on microstructure, electronic properties, and dielectric behaviors are illustrated, and the application progress of fluorinated boron nitride nanosheets in electronic packaging, energy-storage insulation, high-voltage composites, lubrication, and spectroscopic sensing is reviewed. Material performance does not increase monotonically with fluorine content but is jointly governed by the fluorination chemical state, lattice defects, and interfacial conditions. Current challenges include difficulties in precise fluorination control, insufficient quantitative structure-activity relationships, scarce long-term service data under practical working conditions, and limitations in green large-scale fabrication. Future research should focus on establishing quantitative correlations among fluorination state, interfacial structure, and material performance; developing site-selective, low-damage fluorination techniques; adopting multi-scale interfacial design; and completing engineering-oriented reliability evaluations to promote the practical application of fluorinated boron nitride nanosheets.