In a land area of 24,492 square kilometers, the diocesan territory covers the 14 municipalities in the western part of the province of Pangasinan.
Alaminos is a 1st class city in the province of Pangasinan, Philippines which belongs to Region 1. It is bounded by the municipalities of Sual, Bani, and Mabini. Alaminos city belongs to district one with 39 barangays.
As of year 2018 the total population is 731,190 of which 82.50 percent are Catholics.
The major ethnic group is that of the Ilocanos who comprise half of the area's total population, followed by Pangasinenses with 40 per cent, Tagalog, Zamals and Bolinaos with the remaining 10 per cent. There are 15 tribal groups of Igorots in the mountains of the diocese, driven south from the northern parts of the country by militarization, eviction by loggers, and by other government projects, and they have finally settled in the mountains of western Pangasinan.
Alaminos is strategically located in the western part of Pangasinan. From any point of direction, it is the center of the congressional district. More or less 65 kilometers, from the prime city of Dagupan and also 130 kilometers, from San Fernando, La Union, the Regional Center of Ilocos Region.
It used to belong to the Archdiocese of Lingayen-Dagupan until its creation as a separate diocese in 1985. It is bounded on the east by the Lingayen Gulf and the Archdiocese of Lingayen-Dagupan, on the north and west by the China Sea, and on the south by the borders of Zambales and Tarlac Provinces. The whole diocese is a panorama of hills and valleys surrounded by bodies of water. The famous Hundred Islands, a tourist attraction, is found in the vicinity of Alaminos town.
January 12, 1985 was the day when Alaminos, once called the "Wild West of Pangasinan," was created into a diocese by Pope John Paul II. On April 22, L'Osservatore Romano announced the appointment of then Auxiliary Bishop of the Archdiocese of Lingayen-Dagupan, the Most Reverend Jesus A. Cabrera, D.D., PhD, as the First Residential Bishop of the newly created diocese. On June 28, 1985 the new bishop was installed.
The website of Diocese is available at: www.dioceseofalaminos.org
Literacy rate (simple literacy) is 95.45 percent.