Amidst the escalating impact of climate change, the agricultural sector faces the challenge of maintaining productive capacity while conserving increasingly scarce water resources. Modernizing irrigation systems by replacing inefficient open‐channel distribution infrastructures is crucial to address this challenge. Cost–benefit analysis (CBA) offers a valuable tool to assess the effectiveness of such actions, in terms of both financial and socio‐environmental impacts. CBA is also valuable for optimizing the allocation of limited financial resources to the most impactful measures and addressing trade‐offs within the water‐energy‐food (WEF) nexus. This study applies CBA to two modernization projects in the ‘Villalar de los Comuneros’ irrigation district in the Duero River Basin, located in northern Spain. The first project focuses on enhancing energy efficiency by installing a photovoltaic system to power irrigation pumps, while the second promotes climate‐smart agriculture through the use of soil moisture sensors to improve irrigation precision and facilitate the transition to higher value crops. The results of the CBA demonstrate the financial and economic viability of both projects, highlighting the social and environmental benefits generated, and providing policymakers with a valuable framework for guiding similar future interventions.