Quirino has six municipalities: Cabarroguis, the capital town, Saguday, Diffun, Maddela, Nagtipunan, and Aglipay. The province has one congressional district and 110 barangays.

Nagtipunan, officially the Municipality of Nagtipunan, is a 1st class municipality in the province of Quirino, Philippines. According to the 2020 census, it has a population of 25,399 people. Nagtipunan is the largest town in terms of land area in Quirino and the entire Luzon island.

Aglipay, officially the Municipality of Aglipay, is a 3rd class municipality in the province of Quirino, Philippines. According to the 2020 census, it has a population of 30,714 people. Aglipay is 9 kilometres from Cabarroguis and 371 kilometres from Manila.

Maddela, officially the Municipality of Maddela, is a 1st class municipality in the province of Quirino, Philippines. According to the 2020 census, it has a population of 40,943 people. Maddela is the commercial hub of the province. It is between the provinces of Isabela and Aurora.

Diffun, officially the Municipality of Diffun, is a 2nd class municipality in the province of Quirino, Philippines. According to the 2020 census, it has a population of 56,102 people.

Cabarroguis, officially the Municipality of Cabarroguis, is a 3rd class municipality and capital of the province of Quirino, Philippines. According to the 2020 census, it has a population of 33,533 people.

Saguday, officially the Municipality of Saguday, is a 5th class municipality in the province of Quirino, Philippines. According to the 2020 census, it has a population of 17,137 people.