The synthesis, structure and fluoride sensing of core-substituted naphthalene bisimide are reported. The naphthalene bisimide 1 containing four bromide atom-substituted aromatic core and two hydrophobic n-octyl termini adopts an extended structure and self-assembles through non-covalent interactions to form unbranched fibers. X-ray crystallography confirmed the existence of multiple C=O....Br halogen bond-mediated supramolecular sheet-like assembly of the core-substituted naphthalene bisimide 1. The naphthalene bisimide 1 exhibits different backbone contortion in the central aromatic core in crystals obtained from chloroform, ethyl acetate and tetrahydrofuran. Moreover, in aqueous medium the core-substituted bisimide 1 acts as a turn-on fluoride sensor by anion-π interaction and charge transfer. Finally, we fabricated a paper strip printed with the naphthalene bisimide 1 for use as a cheaper and instant naked eye sensor for fluoride in aqueous medium.