Cancer is an extremely significant disease that profoundly impacts human survival and quality of life. Researchers have been searching for effective therapies, among which metal/organic hybrid nanomaterials received widespread attention due to their tumor imaging and treatment capabilities. Metal/organic hybrid nanomaterials are easy to modify and possess magnetic and plasma resonance, catalytic function, and biological activity. Then, researchers have recently designed a series of highly efficient metal/organic hybrid nanomaterials with integrated theranostics, good biocompatibility, and relative safety for achieving excellent therapeutic outcomes in cancer combined with various treatment methods. This paper highlights the research progress of metal/organic hybrid nanomaterials in the single diagnosis and treatment of cancer and their integration into diagnosis and treatment. The development trends, key problems, future outlook, and challenges of metal/organic hybrid nanomaterials are summarized and discussed. It is expected that the metal nanoparticles discussed in this paper can provide insights into the early diagnosis and effective treatment of cancer.