Recognition of multiple knowledge systems is essential to facilitate collaboration and mutual learning between different actors, integration across social and ecological systems, and sustainable development goals. This study aims to identify how local knowledge from the indigenous people in developing countries contributes toward supporting the social–ecological system. We use a case study of the Ammatoa community, one of the indigenous communities in South Sulawesi Province, Indonesia. This study shows how their social and ecological practices are combined to develop their customary area and how the Ammatoa’s customary values contribute towards achieving Sustainable Development Goals (SDGs) 15 and 12 of the United Nations, i.e., leveraging local resources for livelihood and ensuring sustainable consumption and production patterns. Examples of practices elaborated in this paper are protecting, restoring, and promoting sustainable use of terrestrial ecosystems, sustainably managing forests, combating desertification, halting and reversing land degradation, halting biodiversity loss, and ensuring sustainable consumption and production patterns. Furthermore, the Ammatoa’s customary values form a sustainable system that not only affects their social aspects, but also their economy and surrounding environment. This research can be used to develop relevant environmental-related interventions related to SDGs 15 and 12 from indigenous peoples’ perspectives.