On February 16, 1984, Pope Joh Paul II created the new Diocese of Mati, taking part of its territory from that of the Diocese of Tagum.  In November of the same year, the Most Reverend Patricio Alo, until then the Auxiliary Bishop of Davao, was appointed First Bishop of Mati.  Meanwhile the Diocese of Davao had become an archdiocese, and Tagum and Mati were made its suffragans.

The Diocese of Mati today comprises the civil province of Davao Oriental, the easternmost portion of the Old Davao Province.  It covers a land area of 5,146 square kilometers and a population of 445,861 of which 86 per cent are Catholics.  Its titular patron is San Nicolas de Tolentino.  It has supervision over 15 parishes run by 39 priests.  It has 660 Basic Ecclesial Communities.

The faithful of the Diocese of Mati envision for themselves a full Christian maturity, giving Christian service to all, especially the poor and the oppressed, in accord with the Gospel Words of Jesus Christ.

The Christianization of the Davao area in Mindanao is attributed to the arrival in the area of the Augustinian Missionaries in 1848.  This was followed by the Jesuits and the PIME Fathers of Quebec.  But it was the Maryknoll Fathers who finally arrived in the area in 1958 and settled down to the arduous task of evangelizing the inhabitants.

Early Spanish exploration of the Davao area can be traced back to 1528 when Saavedra visited the Sarangani Islands on the southwestern entrance to the Davao Gulf.  He coasted along the shores of Davao Oriental where he established the first settlement, that of Caraga.

The early missionaries later settled in places like Caraga, Baganga, Cateel and the nearby areas, baptizing, giving the sacraments, building churches and convents.  Some of these old structures can still be found today, and some of them are still serving their Christian communities.

The entire Davao Province was politically subdivided into three in 1967.  From this subdivision emerged the provinces of Davao del Norte with Tagum as its capital, Davao del Sur with Digos as capital, and Davao Oriental with Mati as capital.

Ecclesiasticall the entire Mindanao area was under the Diocese of Cebu since 1595, until some parts were placed under the jurisdiction of Jaro in 1865.

In 1910 the Diocese of Zamboanga was created and took all ecclesiastical territories in Mindanao away from Cebu.  Other dioceses were established over the years, including the then Prelature of Davao which eventually became a diocese.  In 1962 the Prelature of Tagum was created, taking its territory mostly from the then Prelature of Davao.