<p>Nanotechnology is rapidly transforming numerous sectors, especially biomedicine, enabling advancements in precision diagnostics, targeted drug delivery, and innovative therapies. Among the vast array of nanomaterials, nanoscale metal–organic frameworks (NMOFs)—a unique class of metal–organic frameworks—show immense promise for biomedical applications. This is due to their exceptional properties, including a high surface area-to-volume ratio, significant porosity, adjustable pore sizes, and flexible functionalization capabilities, all of which make them ideal for interacting with biological systems. This review offers a detailed look into NMOF synthesis, highlighting four main methods: solvothermal, reverse microemulsion, microwave-assisted, and ultrasonic synthesis, noting that the reverse microemulsion approach tends to be more intricate than the others. We then explore the diverse biomedical uses of NMOFs, spanning diagnostics, therapeutics, and theranostics. In diagnostics, NMOFs significantly improve imaging accuracy, as their integrated metal ions act as effective contrast agents for various imaging techniques, such as magnetic resonance imaging (MRI), optical imaging, and X-ray computed tomography (CT). For therapeutic applications, NMOFs demonstrate considerable potential as targeted drug delivery vehicles, particularly in cancer treatment, utilizing both in situ and post-encapsulation methods. Finally, we showcase the theranostic capabilities of NMOFs, which refers to their impressive ability to combine both diagnostic and therapeutic functionalities within a single platform, paving the way for truly multifunctional approaches to disease management.</p>