This chapter proposes a comprehensive and participatory methodology for the preliminary design and impact assessment of cultural projects in rural areas, addressing the lack of specific tools for early-stage planning in low-density territories. It draws from user-centered design, service design, and open innovation to formulate a replicable and context-sensitive approach that integrates local needs from the outset. The methodology emphasizes the role of the preliminary design phase as a strategic moment to define which qualitative and quantitative indicators should be considered when measuring the impact of cultural projects across the three dimensions of sustainability: social, economic, and environmental. This methodological proposal builds on previous studies that have addressed this task from various perspectives, and are here synthesized and organized specifically in relation to cultural projects developed in rural areas. Through a systematized process based on community participation, impact measurement, and institutional collaboration, the chapter contributes to the professionalization of cultural project design in rural contexts. This methodological innovation offers significant flexibility, allowing its adaptation and replication across a variety of rural settings, thus providing researchers and practitioners with a practical tool to manage and assess the complexity inherent in cultural initiatives in these territories. Ultimately, the proposed approach reinforces the role of culture as a driver of sustainable development and territorial cohesion while promoting inclusive and sustainable growth with potential for international application.