The current study reports on the indigenous ethnomedicinal knowledge and practises of the Adis in two villages of the Upper Siang district of Arunachal Pradesh. Extensive personal interviews, concrete case studies, and participant observation were used to collect data in the year 2021. Herbal medicine, as well as magico–religious–spiritual practises, are part of the Adi ethnomedicinal system. A variety of medicinal plants grown locally are used to treat a wide range of ailments. The use of more than one medicinal plant species for remedy preparations is more common than the use of a single species. Plant species are identified using relevant and standard literature and presented with their scientific names, family names, English and vernacular names, part or parts used, and modes of administration in the target disease. The current study was carried out to better understand floral resources, as well as their use as ethnomedicine by the Adis in their indigenous knowledge system.