Nanosensors are nanoscale component devices designed to detect a specific molecule, biological factor, or environmental condition. Compared to their macroscale analogues, these sensors are highly precise, portable, economical, and detect at a far lower level. The need for nanostructured sensors to identify and measure physical and chemical features as well as properties of sophisticated biological and industrial systems has led to a growth in importance in their commercialization. In this chapter, we will discuss different routes to fabricate polymer-based nanosensors and also various applications for their usage in industry like; chemical, optical, medicinal, food, textiles, and electronics. Particularly exciting uses for nanosensors include; chemical detection, food and water quality monitoring, and medical diagnostic applications. 2030 sustainable development goals have the potential to be successfully implemented with the help of nanosensors technology. However, the commercial impact of nanosensors has been diminished by a lack of knowledge about the health impacts of these materials and the expensive cost of some of the basic ingredients needed.