Debris flows are one of the most dangerous types of mass movements due to their extremely rapid evolution, long travel distances, and significant impact forces. Structural measures, together with mapping and land use planning, are usually deployed to mitigate the effects of such events on relevant areas. These structures can also be used to collect relevant information regarding the occurrence of potentially critical events to activate appropriate countermeasures to ensure people’s safety. The monitoring system presented in this paper is designed to be installed on flexible barriers, a widespread intervention to deal with debris flows. The system is composed of a wide range of different sensors, following a multi-parameter approach, to validate the collected data and disseminate accurate information concerning the ongoing event. Exploiting IoT-based communication technologies and automatic procedures for data acquisition and elaboration allows for the identification of the impacts on the barrier with a real-time approach, activating appropriate actions to mitigate the related risk. Two different events are presented, involving a system installed near the A27 Highway in Northern Italy, highlighting the system’s reliability and effectiveness in detecting potentially critical events.