Nanotheranostic is a boon of nanotechnology, which combines therapy and diagnosis to locate, treat and monitor disease progression to provide customized medicine based on individuals’ biological profiles. The intrinsic unique properties of organic, inorganic, and biomimetic nanovectors offer a great opportunity to engineer advanced theranostic platforms to diagnose, target, and treat life-threating diseases such as cancer, infectious diseases, cardiovascular diseases, and central nervous system-associated disorders. The size, shape, and surface properties, of nanovectors, make them suitable for designing theranostics that can enter blood-brain barriers and deliver therapeutics with fewer side effects. Engineering nanovectors that work under external or internal triggers allow controlled drug release, stability, and an extended half-life in body systems. Furthermore, nanotheranostics vectors developed using biomarkers of target cells or tissues provide a huge advantage to utilize them in more than one imaging method and therapeutics. Though polymeric, magnetic, and quantum dots ruled theranostic applications earlier, now nanovectors developed using iron oxide or gold taking their place in several theranostics platforms and have shown promising results on several disease conditions lately. Certain nanovectors exhibit toxic profile and coating of such vectors with biocompatible and biodegradable polymers offer benefits via mitigating toxicity. To make theranostic application a reality for humans, much care and knowledge of biological systems and their behavior with multifunctional nanovectors have to be expanded and addressed thoroughly. © 2023 Elsevier Inc. All rights reserved.