In a land area of 3,092 square kilometers, the diocesan territory covers Iligan City and part of the province of Lanao del Norte. The diocese lies in the northern part of Mindanao, where the Zamboanga Peninsula joins with the mainland of Mindanao between Yllana and Iligan Bays.
In Iligan Diocese the population is 1,551,000 at end of 2016.
Ecclesiastically, all of Mindanao and Sulu came under the jurisdiction of the Diocese of Cebu during the Spanish era. When the Diocese of Zamboanga was created in 1910, it had jurisdiction over the whole of Mindanao. In 1933 the Diocese of Cagayan de Oro was separated from that of Zamboanga and got jurisdiction over Surigao, both Misamises, Bukidnon, and part of the old Lanao, presumably the northern part nearer to it. In 1971, Iligan became a prelature nullius and suffragan of the Archdiocese of Cagayan de Oro.
The Prelature of Iligan was created on Feb. 17, 1971, with the late Bishop Bienvenido S. Tudtud as the first Prelate Ordinary. In November of 1982, Iligan was elevated to a diocese, suffragan first to the Archdiocese of Cagayan de Oro and later to the Archdiocese of Ozamiz. Bishop Fernando R. Capalla was named first Bishop of the Diocese of Iligan. In 1995, Monsignor Emilio L. Bataclan became the second bishop of the diocese.
For the church in Iligan it has been a slow process of development considering the existing situation of Christians and Muslims co-existing in the area. In its first stage of development, the church in Iligan was more concerned with a genuine dialogue between the faiths.
The second stage was the establishment of Basic Ecclesial Communities to bring evangelization down to grass roots level, in line with the spirit behind the Second Plenary Council of the Philippines (PCP-II).
Major Industries in Iligan Diocese are Cement, Oil, some Chemicals, steel and electricity. The agricultural sector comprises rice, corn, root crops, vegetables, fruits, flowers, livestocks, etc.
The literacy rate is 90 percent.