Precise diagnosis of a disease is paramount for effective early treatment and the prevention of further complications. Antigens, enzymes, and proteins present in human bodily fluids as a result of infection can serve as potential hallmarks, or biomarkers, for specific diseases, aiding in diagnosis. Traditional biosensors, while widely used, have limitations, including high sample volume requirements, low sensitivity, and a purely indicative nature, often requiring further confirmation. This process is time-consuming and not cost-effective. Nanotechnology-based solutions address these limitations. The continuous development of novel nanomaterials offers faster detection, requires smaller sample sizes, and provides high precision, making them suitable for detecting a wide range of diseases, including bacterial, viral, and fungal infections. Beyond infectious diseases, these technologies can also detect conditions such as diabetes, cancer, and Alzheimer’s disease. While a comprehensive study of all biomedical applications of nanobiosensors is beyond the scope of this chapter, we will focus on their use in the diagnosis of HIV, Alzheimer’s disease.