Nature conservation efforts cannot succeed without stakeholder participation. The inherent complexity of nature-based ecotourism has made the development of sustainable ecotourism operations a challenge, so it is essential to increase community stakeholder participation. Hence, this study investigates local community participation in Lar National Park (LNP) and the Jajrud Protected Area with the Sustainable Use of Natural Resource Areas (JPA) in Iran and evaluates how this influences the sustainability of ecotourism. This study found that in LNP, sustainable ecotourism development involving local communities is increasing because of the high level of attachment and interest to this part of pristine nature. In the JPA, the relationship between local community participation and ecotourism sustainability is significant too. As a result, natural habitats have been degraded and sustainability has decreased. To conserve these critically endangered natural areas, managers and decision-makers must increase community participation and education to encourage local communities to engage more in developing sustainable ecotourism.