The City of Ilagan is located approximately between 17 degrees, 2 minutes and 17 degrees, 14 minutes north latitude and 121 degrees, 45 minutes and 122 degrees, 30 minutes east longitude (17°08’N, 121°53’E).
Ilagan is approximately 96 kilometers from Tuguegarao and 130 kilometers from Bayombong. It is 292 air kilometers North of Manila and is linked with the metropolis by the National Highway via Sta. Fe. By this Highway, the distance between these two points is about 400 kilometers.
The City of Ilagan is located on the central portion of the province of Isabela. It is bounded by nine (9) municipalities: on the north by the municipalities of Divilacan, Tumauini, and Delfin Albano; on the west by the municipality of Quirino; on the east by the municipalities of Divilacan, Palanan, and the Pacific Ocean; and on the south by the municipalities of Gamu, Naguilian, Benito Soliven and San Mariano.
Ilagan has a vast area of 116,626 hectares based on data from the Coordination Board. It is the largest city of Isabela comprising 9.39% of the province. Based on the 2008-2012 City of Ilagan Comprehensive Land Use Plan, of the total 116,626 hectare land area; 22.32% are agricultural, 61.78% are forest areas and the remaining 15.9% are build-up areas and open grassland areas that are available for industrial, commercial and residential uses.
Of all cities in the country, Ilagan ranks as the top producer of corn. As an agriculturebased city, it produces ample supply of corn, rice, vegetables and legumes. Fruits like the banana are year-round products especially in the mountainous areas of the city. The City of Ilagan also produces seasonal fruits such as mangoes and pomelo. The Cagayan Valley Integrated Agricultural Research Center (CVIARC) is the primary plant breeding institution in Region 02. It is located in Barangay San Felipe along the National Highway. The City has rich forest resources. Hectares of forest land are strictly protected by authorities like the Department of Environment and Natural Resources (DENR), several NGOs and the Local Government Units (LGU).