Density functional theory calculations have been performed to study the adsorption behavior of ionic liquids (ILs) on 15th group nanosheets including phosphorene (BP), arsenene (As), and antimonene (Sb). Three ILs based on 1‐ethyl‐3‐methylimidazolium ([EMIM]+), tetramethylammonium ([TMA]+), and N‐methylpyridinium ([MPI]+) cations paired with tetrafluoroborate ([BF4]−) anion were selected as adsorbates on different 2D nanosheets to explore the interfacial behavior. The calculated structural, energy, charge transfer, and electronic properties of the adsorption systems for ILs/nanosheets exhibit combination by non‐covalent interaction. Adsorption of ILs induces a very small reduction of band gap for BP, As, and Sb nanosheets, and the electronic properties of nanosheets are nearly unchanged. These results increase understanding of the experimental mechanism for IL dispersion 2D materials and suggest that ILs can be used to functionalize elemental 15th group nanosheets for further applications in various fields.