The blood-brain barrier (BBB) prevents the transfer of many therapeutic drugs across the brain. Therefore, the leading treatment strategies of Alzheimer's disease (AD) are often unsuccessful. Another challenge is to achieve specific targetability across BBB and diagnosis. Herein, theranostic-based strategies are emerging in order to combine therapeutic, targeting, and diagnostic capabilities. Recent nanotechnological advancements enable a common platform for the formulation and development of efficient theranostics. This can be attained by engineering some of the properties of nanomaterials, thus enabling them to become efficient and suitable theranostics. In this review, we discuss the various novel approaches of theranostic nanomaterials owing to multimodal functionality across the brain as an effective and probable treatment as well as early (timely) diagnosis of Alzheimer's disease. In this respect, we conducted a PubMed search to review the latest development in theranostic nanomaterials, especially for Alzheimer's (major type of dementia) therapy that led us to discuss the present theranostic nanomaterials utilizing drug carriers that include cargo, targeting ligands, and imaging agents for delivery to particular tissues, cells, or subcellular components. Our focus is on strategies for syntheses, but we will also consider the challenges and prospects associated with this evolving technology. The current review includes knowledge of the history, overview of AD, and therapeutics with a future approach of using theranostic nanomaterials as personalized medicines.