Nanosized metal oxides have immense potential encompassing various areas of contemporary research, which is not observed in the conventionally available bulk metal oxide materials. Metal oxide nanomaterials occupy a prominent position within the broad field of nanomaterials that have been utilized in biomedical applications, including biosensing, immunotherapeutics, drug delivery, regenerative medicine, bioimaging, wound healing, and so on. Transition metal oxides and their engineered composites having applications including diagnostics and therapeutics have been covered in this review. These materials are in the cusp of cutting-edge research in order to address challenges in real-life clinical applications, in addition to the investigations into their biocompatible synthetic strategies, including effects of their size, morphology and so on, that might result in short- or long-term health complications. A proper understanding of the changes in the signaling pathways associated with cell cycle, migration, differentiation, proliferation triggered by metal oxide nanoparticles is expected to be the harbinger of an era of personalized medicine for effective and targeted therapeutic applications.