Recently, engineered metal nanoclusters have gained great attention in the field of nanobiomedicine and clinical diagnosis due to their special properties and potential utilizations. These nanoclusters typically consist of a small number of metal atoms organized in a unique configuration, leading to distinct electronic, optical, and magnetic properties. One of the most developing fields in which engineered metal nanoclusters were applied is the medical domain. Herein we will focus on the utilization of these nanostructures in the three main branches of this domain, nanodiagnostics, nanotherapeutics, and nanotheranostics. Concerning the field of nanodiagnostics, we will shed light on the application of metallic nanoclusters in molecular imaging and the diagnosis of several diseases like cancer, infectious illnesses, metabolic disorders, neurological diseases, and cardiovascular ones. On the other hand, we will define the concept of nanotherapeutics and introduce the three types of drug targeting utilizing special nanoplatforms integrating the metallic nanoclusters. Finally, the new concept of the nanotheranostics will be presented.