The Northern Sierra Madre Natural Park lies in the midsection of the Sierra Madre mountain range which stretches from the province of Aurora to Cagayan. It consists of of land area and of coastline water area corresponding geographically with the Isabela municipalities of Palanan, Divilacan and Maconacon, as well as portions of San Mariano, Dinapigue, San Pablo, Cabagan, Tumauini and the city of Ilagan. It is bounded on the north by the Dikatayan River, on the south by the Disabungan River, on the west by Cagayan Valley, and on the east by the Philippine Sea.