The use of Carbon Nanotubes (CNTs) to develop various sensing prototypes has been a revolution in the field of microelectronics. CNTs have been synthesized in different physiochemical forms, and subsequently, utilized to fabricate sensors with enhanced electrical, mechanical and thermal characteristics. These CNTs-based sensors have been employed for biomedical, environmental and industrial applications; this chapter provides an overview of CNTs, the methods involved in their synthesis, and a spectrum of their application. Some of the primarily focussed sectors where these sensors have been used are as electrochemical, strain, bio and energy-harvesting sensors. It also explains some of the challenges posed by the current sensors, along with their possible remedies.