[1] During a visit to the United States he was called by the Catholicos-Patriarch, Mar Dinkha IV, to serve the Assyrian Church of the East in the ordained ministry.
[1] During Gewargis's metropolitanship he established the archdiocesan minor seminary in Baghdad, which produced numerous priests and deacons for Iraq.
While in Baghdad, he established the Metropolitan's Press, and had a number of liturgical books and other volumes of a catechetical nature printed for worldwide use.
On 18 September 2015, the Prelates elected Mar Gewargis Sliwa as the 121st Catholicos-Patriarch of the Holy See of Seleucia-Ctesiphon.
[1] On 6 September 2021, Mar Gewargis III formally stepped down as Catholicos-Patriarch during an Extraordinary Session of the Holy Synod of the Assyrian Church of the East, leaving the Patriarchal See vacant.
On 8 September 2021, the Holy Synod elected Mar Awa III Royel, Bishop of California and Secretary of the Holy Synod, to succeed Mar Gewargis III as Catholicos-Patriarch of the Assyrian Church of the East.