San Pablo is a coastal municipality in the province of Isabela. The municipality has a land area of 637.90 square kilometers or 246.29 square miles which constitutes 5.14% of Isabela’s total area. Its population as determined by the 2015 Census was 25,384. This represented 1.59% of the total population of Isabela province, or 0.74% of the overall population of the Cagayan Valley region. Based on these figures, the population density is computed at 40 inhabitants per square kilometer or 103 inhabitants per square mile.

San Pablo located at 17°28′N 121°59′E is bounded by Tuguegarao City in the north, the Municipality of Maconacon in the east, the Municipality of Cabagan in the south and the Cagayan River and Municipality of Santa Maria in the west. It is subdivided into 17 barangays and has a land area of 637.9 square kilometers with a population of 25,384 in 2015. The highest point of the province is located near the border with Cagayan. Mount Dos Cuernos peak has an elevation of 1,785 metres (5,856 ft) located in San Pablo near the border with Maconacon. The Baka (Cow) Festival established in 2004, during the tenure of Mayor Antonio N. Miro, is observed annually every January 15 during the patronal town fiesta to promote the cow industry and its by products.