Nanozymes, synthetic nanomaterials mimicking enzyme properties, have revolutionized the field of diagnostics and therapeutics. This chapter explores the diverse enzymatic activities of nanomaterials and their recent advancements in the development of sensors for the detection of several diseases and therapeutic interventions. Compared to the traditional enzyme-based assays, the nanozymes offer superior specificity, sensitivity, and stability, thereby transforming the biosensing and treatment methodologies. Their application spans pathogen, biomolecule, and environmental-contaminant detection, fostering rapid and precise diagnostic platforms applicable in point-of-care testing, food safety monitoring, and environmental surveillance. In therapeutics, nanozymes hold promise in targeted drug delivery, efficient bioactive compound degradation, and modulation of biological processes critical for cancer detection and treatment strategies. They play pivotal roles in enzyme prodrug therapies, nanozyme prodrug therapy for antibacterial measures, and bioconversion of glucuronides, showcasing their versatility in biomedical applications. A wide range of nanomaterials acting as nanozymes, including metal nanoparticles, metal oxide nanoparticles, carbon-based nanoparticles, metal–organic frameworks, and other nanostructures, have been reported for various applications in the field of diagnostics and therapeutics. The nanozymes possess special catalytic qualities that are vital for diagnosing and treating deadly diseases, such as cancer. The combination of nanomaterials with enzyme-mimicking capabilities opens up new avenues for precision diagnostics, tailored medicine, and targeted therapy—a field that is especially important in oncology. In this chapter, the wide array of nanomaterials employed as nanozymes in medicine and diagnosis has been described in detail. Several nanomaterials like metal nanoparticles, metal oxide nanoparticles, carbon-based nanoparticles, metal–organic frameworks, and other nanostructures are investigated for their unique catalytic properties and potential applications in disease identification and treatment, particularly in cancer diagnostics and therapy. The synergistic combination of enzyme-mimicking functionalities and nanomaterials presents novel avenues in targeted therapy, personalized medicine, and precision diagnostics, with profound implications for the biotechnology and healthcare industries.