The nanomaterials that possess the therapeutic and imaging characteristics, and/or have the ability to carrying and co-delivering the active materials (imaging and therapeutic agents) to the diseased sites in the body, are known as nanosensor for drug delivery. This nanomaterial possesses different distinguished properties such as smaller sizes (up-to 100 nm), large surface area to volume ratio, and bio-functionalization characteristics. Therefore, these are used for multiple purposes simultaneously, such as early detecting/diagnosing of diseases, monitoring therapeutic responses as well as show therapeutic efficacy. Moreover, also overcomes the issues related to the delivering of agents (imaging and therapeutic) like poor water solubility, less distribution in the body, deep penetrations into the diseased sites, and the need for the extensive invasive procedures. In this chapter, we have described the fundamentals concept of conventional biosensor and nano (biosensor) along with sensing mechanism of nanomaterials. Furthermore, we have illustrated the designing, formulations and types of materials (metallic and non-metallic) for the development of nanosensor like nanodelivery for drugs (nanotheranostic). Additionally, recent reports for using the nanotheranostic (as diagnostic/therapeutic ability) against diseases such as cancer, cancer, cardiovascular diseases (CVD) and managing the diabetes. Also described the sensing mechanism of these nanotheranostic in response to the available marker in the diseased sites like pH, enzymatic responsive, and ROS-responsive. Additionally, we have discussed in detail the challenges for regulatory of nanotheranostics. Finally, presented the future perspective for clinically translation of these nanotheranostics and also presented the perspectives of nanotehranostics for overcoming the technical, manufacturing, regulating, as well as economic barriers for safe and efficient clinical application.