Barangay San Isidro

Classified as a mid-sized barangay, Barangay San Isidro is one of the administrative divisions of Diffun in Quirino, Cagayan Valley, Philippines.

According to the 2020 Philippine census, Barangay San Isidro had a population of 2,030. This made it the 11th largest of 33 barangays in Diffun by population, placing it in the middle tier of the municipality. Residents of Barangay San Isidro accounted for approximately 3.62% of the total population of Diffun, which stood at 56,102 in the same census year.

Between the 2015 and 2020 censuses, the population of Barangay San Isidro changed from 1,940 to 2,030, a shift of +4.6% over the five-year period. This places the barangay among those with growing populations in Diffun. Barangay San Isidro is officially classified as rural, a designation applied to barangays with lower population density and predominantly non-built-up land use.

Diffun is a municipality comprising 33 barangays, and serves as the governing unit directly responsible for local services in Barangay San Isidro, including public health, sanitation, peace and order, and civil registration. Within the wider province of Quirino, which contains 132 barangays across its component cities and municipalities, Barangay San Isidro ranks 33rd by 2020 population. Quirino is classified as a 3rd by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

The barangay's legislative and executive affairs are handled by a Punong Barangay and the Sangguniang Barangay, elected nationwide during the Barangay and SK Elections. The next BSKE is scheduled for Monday, November 2, 2026, following the synchronized election schedule set by COMELEC Resolution No. 11191.