The Diocese of Tandag was created on June 16, 1978,
carved out of the Diocese of Surigao. On November 7, 1978, Bishop Ireneo Amantillo, CSsR, D.D., was installed as First Bishop of Tandag, a position he holds up to the present
Bishop Amantillo was appointed by Pope John Paul I on September 6, 1978.
The diocese comprises the entire civil province of Surigao del Sur whose capital is Tandag. The province occupies
about half of the eastern coastline of Mindanao facing the Pacific Ocean, just a few miles from the Philippine Deep, one of the deepest ocean depths in the world.
The two Surigao provinces, which were just one province before, are situated on the northeastern portion of Mindanao Island and is part of the Mindanao region known
as Region XI. A political subdivision in 1960 gave to Surigao del Sur the bigger portion.
Surigao was one of the early centers of the faith dating back to 1622 when the
Augustinian Recollects arrived. Earlier the explorer Villalobos had explored the area to subjugate the natives. The missionaries settled in Tandag, Bislig, and later in
Cantillan, earlier known as Caraga. In 1895 the Benedictines came and remained until 1908. Then the Missionaries of the Sacred Heart came. In 1972 most parishes in the area came to be staffed by the diocesan clergy.
The Diocese of Tandag covers a land area of 4,861 square kilometers, and a population of 451,287 of which 84 per cent are Catholics. Its titular patron is San
Nicolas de Tolentino, whose feast is celebrated September 10. The diocese is a suffragan of the Archdiocese of Cagayan de Oro.
Today a majority of the inhabitants are migrants from the northern part of the
country, although the migrants came in limited numbers because of the lack of arable land. The major dialect is Cebuano. The province has vast forest areas; in
the years 1971-1972 it was second only to Davao in log export. Most of its industries are timber-oriented, such as that of the Paper Industries Corporation of
the Philippines (PICOP) based in Bislig. Most fishing is from inland fish-ponds as the coastal waters near the Philippine Deep yield no fish since the place is frequented by earthquakes.
In line with the recommendation of the Mindanao-Sulu Pastoral Conference (MSPC) and by the decrees of the Second Plenary Council of the Philippines, the diocese
has committed herself to the formation of Basic Ecclesial Communities or Gagmay Kristohanong Katilingban (GKK).
With an information drive going on at present on the decrees of PCP II, coupled with
a clarification of the vision-mission statements of the various apostolates at work in the area, the diocese is now pre-occupied with the formation, and later the implementation, of the National Pastoral Plan.
The Diocese of Tandag has 19 parishes within its jurisdiction, administered by 20 diocesan and 3 religious priests, 4 deacons and 25 religious sisters. Among its
Catholic institutions are 3 colleges, 13 high schools, 4 elementary schools and 1 pre-school.