Smart sensing technologies and their inherent data-processing techniques have drawn considerable research and industrial attention in recent years. Recent developments in nanometer CMOS technologies have shown great potential to deal with the increasing demand of processing power that arises in these sensing technologies, from IoT applications to complicated medical devices. Moreover, circuit implementation, which could be based on a full analog or digital approach or, in most cases, on a mixed-signal approach, possesses a fundamental role in exploiting the full capabilities of sensing technologies. In addition, all circuit design methodologies include the optimization of several performance metrics, such as low power, low cost, small area, and high throughput, which impose critical challenges in the field of sensor design. This Special Issue aims to highlight advances in the development, modeling, simulation, and implementation of integrated circuits for sensing technologies, from the component level to complete sensing systems.