Tourism as a tool for the enhancement and conservation of heritage represents an opportunity for many managers of cultural properties. However, despite the numerous works developed so far on tourism governance, the elaboration of preliminary studies for decision-making in heritage buildings is still a challenge. Considering the ecosystem services approach, an index is proposed which allows tourism and cultural heritage managers to analyze and quantify the level of tourist exploitation (use) of a monument for the services (benefits) that it offers to society. In this paper, a multi-criteria evaluation system was proposed, related to the main use of the building and its relationship with various tourism components, which have been classified as cultural, leisure, recreational, lodging, catering, intermediation, transportation, and event organization. The model has been applied to the Parroquia del Mar (Alicante, Spain) of great cultural relevance, but not exploited for tourism. The results obtained demonstrate the usefulness and validity of the model, considered as a tool capable of bridging the gap between heritage conservation and its touristic use, highlighting the importance of the services offered as necessary attributes for its (re)valuation, combining the social benefits of its exploitation, its touristic use and the awareness of its conservation and protection.