Nitric oxide (NO) is an air pollutant known to adversely affect the environment, humans, and other living organisms. Low-level NO gas is also created by human bodies and emitted as a component of exhaled breath and skin gas under some health conditions. Therefore, there is a strong demand for the monitoring of NO gas concentration. In this paper, we present novel NO gas sensors that have been developed using multilayered WO3-based thin films with interspaces. Ag doping into a WO3 thin film is effective in increasing the sensitivity to NO. Multilayered thin-film sensors with interspaces successfully enhance both sensitivity and selectivity to NO. The developed sensor with quadruple-layered sensing films can detect as low as 0.5 ppm NO gas with good selectivity at an operating temperature of 290 ℃. The response and recovery times are 81 and 138 s, respectively, for the double-layered sensor, while its sensitivity is lower than that of the quadruple-layered sensor. Thus, the sensors are promising as a portable and inexpensive NO sensing device in various application fields such as environmental monitoring and health diagnosis.