Jonai is the easternmost sub-division of Dhemaji District, about 554 Km. away from the state capital, Guwahati. Covering a total Geographical area of 1111.81 Sq. Km, it is bounded by Arunachal Pradesh in the north, Lali & Brahmaputra River in the south, Sipiya river & Sadiya Subdivision of Tinsukia district in the east and Simen River in the west. The Head Quarter is located at 95.160 E and 27.770 N.

             The Sub- division comprises with one Development Block named by Murkong Selek Tribal Development Block, One Revenue Circle named by Jonai Revenue Circle and 15 Nos. of Gaon Panchayats.