In 1947—at the age of eleven—he was entrusted to the care of Mar Yousip Khnanisho, Metropolitan and the Patriarchal representative for all Iraq, the second-highest-ranking ecclesiastic of the Assyrian Church of the East.

Mar Dinkha's priesthood as Metropolitan of Iran and Tehran[2] reestablished a line of succession which had ceased to exist after the 1915 assassination of his predecessor.

In 1976, the prelates of the church convened in London to elect a new Catholicos Patriarch and chose Mar Dinkha as the most qualified candidate to fill the post.

He also announced that the hereditary line of succession for the Patriarchy which had existed for 500 years[6] was discontinued with his tenure, allowing any cleric from the Church of the East to be elevated to Catholicos-Patriarch.

[9] In 2005, the Patriarch conducted discussions with President of Iraqi Kurdistan Masoud Barzani on returning to the Apostolic See in northern Iraq and constructing a new residence in Ankawa.

A ceremony was held at St. George Cathedral in Chicago, where a portion of Ashland Avenue was renamed "His Holiness Mar Dinkha IV Blvd".

[20] On 29 November 1996, Dinkha signed an agreement of cooperation with the Patriarch of Babylon of the Chaldean Catholic Church—Raphael I Bidawid—in Southfield, Michigan[17] and met again on 16 August 1997, to bless an Assyrian church.

As a product of this process, Dinkha entered into negotiations with the Syriac Orthodox Patriarch Mar Ignatius Zakka I Iwas in 1997 and the two churches ceased anathematizing each other.

[28] In September 2006, Mar Dinkha IV paid a historic visit to northern Iraq to give oversight to the churches there and to encourage the president of Iraqi Kurdistan to open a Christian school in Erbil.

He sought to de-politicize the office of Catholicos-Patriarch and expanded the church's outreach to the youth by including non-Syriac liturgies composed in local languages.