To　adapt　to　the　trend　of　increasing　miniaturization　and　high　integration　of　microelectronic　equipments,　there　is　a　high　demand　for　multifunctional　thermally　conductive　(TC)　polymeric　films　combining　excellent　flame　retardancy　and　low　dielectric　constant　(Ε).　To　date,　there　have　been　few　successes　that　achieve　such　a　performance　portfolio　in　polymer　films　due　to　their　different　and　even　mutually　exclusive　governing　mechanisms.　Herein,　we　propose　a　trinity　strategy　for　creating　a　rationally　engineered　heterostructure　nanoadditive　(FG@CuP@ZTC)　by　in　situ　self-assembly　immobilization　of　copper-phenyl　phosphonate　(CuP)　and　zinc-3,　5-diamino-1,2,4-triazole　complex　(ZTC)　onto　the　fluorinated　graphene　(FG)　surface.　Benefiting　from　the　synergistic　effects　of　FG,　CuP,　and　ZTC　and　the　bionic　lay-by-lay　(LBL)　strategy,　the　as-fabricated　waterborne　polyurethane　(WPU)　nanocomposite　film　with　30　wt%　FG@CuP@ZTC　exhibits　a　55.6%　improvement　in　limiting　oxygen　index　(LOI),　66.0%　and　40.5%　reductions　in　peak　heat　release　rate　and　total　heat　release,　respectively,　and　93.3%　increase　in　tensile　strength　relative　to　pure　WPU　film　due　to　the　synergistic　effects　between　FG,　CuP,　and　ZTC.　Moreover,　the　WPU　nanocomposite　film　presents　a　high　thermal　conductivity　(λ)　of　12.7　W　m−1 K−1　and　a　low　Ε　of　2.92　at　106 Hz.　This　work　provides　a　commercially　viable　rational　design　strategy　to　develop　high-performance　multifunctional　polymer　nanocomposite　films,　which　hold　great　potential　as　advanced　polymeric　thermal　dissipators　for　high-power-density　microelectronics.　(Figure　presented.)　©　The　Author(s)　2025.