<p>This study develops a quantitative framework to assess how Nature-Based Solutions (NbS), implemented through agroecological practices, perform within the Water–Energy–Food–Ecosystems (WEFE) Nexus. While NbS are widely recognized for their environmental benefits, few studies provide operational tools to quantify their cross-sectoral trade-offs at the farm level. To address this gap, an intensity-based WEFE assessment and a composite WEFE Nexus Index were applied to a rainfed vineyard in Northern Spain and compared with prevailing conventional practices. The analysis integrates water, energy, carbon, and productivity indicators to reveal nexus interactions rather than sectoral footprints. Results show that the transition to agroecological practices reduces energy demand by 72% and carbon emissions by 57%, demonstrating pronounced water–energy–carbon interdependencies within the WEFE Nexus framework. However, lower yields introduce food–resource trade-offs, highlighting the need to balance environmental efficiency with productivity. These interactions are captured through the WEFE Nexus Index, which provides a systemic performance indicator. The findings demonstrate that agroecological NbS can significantly reduce resource dependency while maintaining viable production, offering both environmental and economic resilience. The study provides a practical methodology for integrating NbS into WEFE Nexus planning and policy at the farm scale.</p>