Mountain huts, crucial to alpine and nature-based tourism, support over 100 million visitors annually, reflecting the sector’s rapid growth. However, these structures, often aged and underperforming, face significant challenges due to increasing tourist flux and the fragile alpine environment, heavily impacted by climate change. Addressing these issues requires understanding their current sustainability performance to guide renovations and interventions. Mainstream sustainability rating systems, while effective in broader contexts, are not suited to assess the unique characteristics of mountain huts. This paper presents a novel sustainability rating system tailored specifically to mountain huts. Developed by Montana Spa, tested by Politecnico di Milano’s Department of Architecture, Built Environment, and Construction (DABC), and supported by the Italian Alpine Club (CAI), the system was designed to be comprehensive yet easy to apply. CAI’s involvement ensured the system’s alignment with the practical needs of hut management, supporting the refinement of the rating categories through a constant dialogue. The methodology involved a literature review and gap analysis of existing systems, which informed the creation of relevant indicators to mountain huts. The developed rating system was tested on Galassi Hut, a case study chosen for its cooperative management and exemplary practices, leading to framework refinement. This research contributes a practical tool for assessing mountain hut sustainability, supporting evidence-based renovations, and addressing critical information gaps in alpine infrastructure management.