Nature-based Solutions (NbS) play a key role in European climate mitigation and adaptation but can generate both health co-benefits and unintended consequences. As NbS are increasingly implemented, there is an urgent need for evidence-based design and monitoring approaches that reduce maladaptation, especially in the health domain. The LILY Action addresses gaps in NbS–Health frameworks, indicators, monitoring, and equity by bringing together 69 interdisciplinary partners to develop conceptual frameworks, best-practice guidelines, and data platforms. LILY also emphasizes co-production, One Health, inclusiveness, and capacity building, particularly for early-career researchers.