This paper presents the development of the Internet of Things (IoT) System on Waterfall Water Level Monitoring for Warning Phenomena. It aims to prevent injured visitors at a waterfall which warning will be alerted on the increased water level at the waterfall. The incident happened at the waterfall during high water level occur suddenly, where visitors are unknown in the situations. The design system is based on IoT System for Waterfall Water Level Monitoring where water level sensors are used to detect high-level water. The ultrasonic sensor was used in this system where the minimum time delay of the sensor was detected compared with other sensors. The Arduino microcontroller board was used as an interface from a sensor as input and output for data collections. A DC motor was used as a generator to supply voltage. The result of the developed system was analyzed based on time delay and efficiency of water level. The analysis presents the motor rotations increased when the water speed has increased. The supply voltage also increased when the motor rpm is increased. This research is significant as an alert system to most tourists and visitors to the most beautiful waterfall in Malaysia. The alert system is one advantage to reduce death cases that happened at the waterfall which usually happen after rain in the surrounding waterfall. This helps the tourism sectors in developing more visitors to the waterfall places and keep visitors safe with the help of the recent technology can reduce bad incidence.