Black phosphorus (BP) is a two-dimensional (2D) nanomaterial with high charge-carrier mobility, a tunable direct bandgap, and a unique in-plane anisotropic structure; however, the easiness of BP oxidation into P xO y species in ambient conditions largely limits its applications. In this study, modified cisplatin-Pt-NO3 [Pt(NH3)2(NO3)2] is used for surface coordination with BP nanosheets to generate Pt@BP, which maintains the surface morphology and properties of BP nanosheets for more than 24 h in ambient conditions. In addition, Pt@BP interacts with DNA both in vitro and in cell. Pt@BP shows a good cellular uptake rate and significantly increases the drug sensitivity of cisplatin-resistant cancer cell lines (A2780 and HepG2) compared with unmodified cisplatin. Our study is the first attempt to stabilize bare BP with cationic cisplatin species, and the generated Pt@BP could be used for potential synergistic photothermal/chemotherapy of cisplatin-resistant cancer.