Agriculture is one of the most dynamic and productive sectors in the Mediterranean region, but it is also the most vulnerable to water scarcity. Currently, it is facing certain challenges, which compromise the sustainability and environmental impact of our food production system. In response, and to help address this issue, the PRECIMED project has developed a decision support system (DSS) to enhance the efficiency of farmers in their daily tasks, including irrigation and fertilization. The PRECIMED DSS offers end users the opportunity to deploy and integrate a range of IoT devices and web services from different sources, as well as the use of advanced agronomic services. The DSS outputs were tested and validated in four different Mediterranean countries, including Spain, Algeria, Tunisia and Greece, under both greenhouse (protected cropping) and open-field-scale cropping systems.