Nanotechnology is the field of science that investigates materials at the atomic scale and designs mate rials with unique qualities via changes in their molecular features. Nanomaterials, which can participate actively in several industrial sectors, provide numerous advantages across every field. Nanomedicine is a medical application of nanotechnology to improve health. It aims to provide an early diagnosis and targeted treatment of diseases with high efficacy. Theranostic nanoparticles are established by combining diagnostic and therapeutic agents within the same nanoparticle. The imaging agent (diagnostic) offers insights into the location and severity of the pathological cells, while the therapeutic agent (therapy) administers lethal medication dosages to the same affected cells. Theranostic nanoparticles, which can be prepared in many types (iron oxide nanoparticles, polymeric nanoparticles, quantum dots, carbon nanotubes, etc.), can be used in compatibility with imaging devices (Positron Emission Tomography (PET), magnetic resonance imaging (MRI) etc.). These nanoparticles constitute an important target for the treatment of many diseases, such as neurodegenerative disorders, where organ pathology is out of reach without invasive methods. Therefore, this innovative technology, which is capable of diagnosing and predicting illnesses at the molecular level, facilitates early diagnosis and treatment, prevents patients from undergoing unneeded interventions, and diminishes superfluous pharmaceutical expenditures within the healthcare system, thus yielding more effective clinical outcomes. The design of theranostic nanoparticles according to the context dependent necessities is crucial and valuable for the effectiveness of targeted and personalised medicine. In this review, we discuss the types and properties of theranostic nanoparticles, imaging technologies, and their applications in Alzheimer’s Disease treatment.