Most of the population of Arunachal Pradesh is of Asiatic origin and shows physical affinities with the peoples of Tibet and the Myanmar hill region. There are dozens of tribes and subtribes, each with a specific geographic distribution. In western Arunachal Pradesh the main tribes are the Nissi (Nishi or Dafla), Sulung, Sherdukpen, Aka, Monpa, Apa Tani, and Hill Miri.

The Adi, the largest tribal group in the state, occupy the central region. On the left is an example of a tipical Adi village.The Mishmi occupy the northeastern hills, and the Wancho, Nocte, and Tangsa inhabit the southeastern district of Tirap.These tribal groups speak about 50 distinct languages and dialects, belonging mostly to the Tibeto-Burmese branch of the Sino-Tibetan language family. They are often mutually unintelligible and, thus, Assamese, Hindi, and English are used as lingua francas in the region. As a rule, the tribes do not intermarry, and each follows distinct social, cultural, and religious practices. The most common religious practice is animism, in which deities of nature and various spirits are worshiped.

Ritual sacrifice is also common, and the mithun (a domesticated gaur, or wild ox) is especially revered as a sacrificial animal. Hindu beliefs and practices have penetrated the region, especially among populations near the Assam lowlands.

Tibetan Buddhism is found among groups near the Tibetan border, and some tribes along the Myanmar border practice the Southeast Asian form of this religion, Hinayana Buddhism.