As an emerging two‐dimensional material, black phosphorus (BP) has fascinating structure and electronic properties, affording broad applications in field‐effect transistors, optoelectronic devices, energy devices, and biomedicines. However, the lone pair electrons of phosphorus atoms readily react with oxygen, so few‐layer BP is easily oxidized and degraded when exposed to air. Therefore, the ambient stability of BP needs to be enhanced for its potential application. Chemical functionalization is one of the most effective methods for improving the ambient stability of few‐layer BP. In this review, we provide a comprehensive overview of the chemical functionalization of BP, focusing on covalent and noncovalent functionalization and surface coordination. The influence of the functionalization pattern on the electronic properties and ambient stability of BP is summarized. Finally, the challenges and future development of chemical functionalization of BP are discussed.