Recently, an agricultural monitoring system using the Internet of Things has been developed to realize smart farming. The high performance of various sensors in agricultural monitoring systems is essential for smart farming to automatically monitor and control agricultural environmental conditions such as temperature and water level. In this study, we propose resistive water level sensors based on an AgNWs/PEDOT:PSS-g-PEGME hybrid structure to improve the already high conductivity and water stability of PEDOT:PSS. After spin-coating the AgNWs/PEDOT:PSS-g-PEGME hybrid film, a laser treatment method successfully patterns the resistive water level sensor with areas of higher resistance. When water contacts the sensor, the variation in resistance caused by the water level changes the current flow of the sensor, allowing it to be used to detect the water level. Finally, we develop a water level sensor module as a component of the agricultural monitoring system by connecting the sensor to a microcontroller for water level monitoring in real time. The proposed water level sensors may be a new solution for detecting water levels in agricultural monitoring systems.