Festivals of Upper Subansiri district mainly reflect the indigenous tribal culture and traditions of this region. The major festivals of this district of Arunachal Pradesh are Si-Donyi festival, Bori Boot festival, Boori-Yullow festival and Mopin festival. These festivals are celebrated with tremendous fanfare and enthusiasm.

Si-Donyi Festival is celebrated mainly in the month of January every year. It is considered as the most significant festival of the Tagin Tribe who form the largest tribal group in the district. Si-Donyi signifies the Earth and the Sun. The Earth gains the first priority and hence they consider earth as their mother. Si-Donyi festival being conducted on a large scale can not be performed individually because of the huge expenditure involved. Thus, the Tagin tribes celebrate this festival collectively. The local youths work for around a month for the preparation of the festival. The elderly persons from the tribe are responsible for forming the committee that organises the festivals. They also guide the priests in performing the rituals for Si-Donyi puja.

Some of the important mythological dances performed during Si-Donyi festival are -
* Sune-Rabo
* Takar Gene
* Koni-Bokar
* Hoye penam

Boys and girls in colourful dresses perform these dances. People believe that by celebrating the Si-Donyi festival the creators "Si" and "Doni" will be satisfied and will bless the people with good crops and prevent diseases. Si-Donyi festival is described as the festival for prosperity and success.

The Hill Miri Tribe of the Upper Subansiri district solely performs Bori Boot Festival. The festival is usually celebrated in the month of February. Bori Boot means to get together irrespective of the age, sex, caste to hail the spring and successful harvest. The festival also invokes the spirit of Bori boot to bless them with prosperity and free them from diseases of any kind. The young members do all the work under the guidance of elders. The `Nibu` or the priest performs puja as well as conducts sacrifices. The celebration of the festival lasts for three days.

Boori-Yullow Festival is the festival of the Nishing tribe. This festival is usually celebrated in the month of February every year for seeking the blessings of the Almighty God for good health and harvest.

The Galo tribes celebrate Mopin Festival. It is performed during the month of April. This festival invokes the Goddess Mopin to bless the people for their prosperity. Prayers are offered for good harvest and to keep them and their cattle free from any diseases. The `Popir` dance is the most popular dance of this festival. Boys and girls in colourful attire participate in this dancing. Eating and drinking goes on during three days long festival.

All these festivals of the Upper Subansiri district are celebrated for obtaining the blessings of the Almighty for good health and prosperity. Another wonderful aspect about this festival is that people celebrate these festivals collectively irrespective of caste and gender.