This research aims at exploring the impact of active tourism activities on sustainable development dimensions. The methodology applied was based on the Theory of Forgotten Effects, which involves the use of different matrices as a research method representing relationship between different elements. According to experts’ opinions, direct and indirect relationships effects caused by active tourism on sustainable development dimensions were evaluated. Particularly, the elements in the matrices were, on the one hand, types of active tourism activities by natural setting (ground, underground, water, underwater and aerial) and, on the other hand, dimensions of sustainable development goals (economic, social, environmental, cultural and governmental). The use of the Forgotten Effects Theory allowed us to analyse incidence relationships, both direct causalities identified by experts in the first place, and also significant linkages between elements in the matrices which had been overlooked initially but showed a strong incidence after applying the aforementioned research method (indirect causalities). Besides this identification of overlooked incidences or “forgotten effects”, another remarkable contribution of this pioneer work is in the selection of themes or objects of study included in the fuzzy metrics, as no other work relating active tourism activities and sustainable development dimensions was found in the literature.