In 1918 was appointed as assistant to the Patriarch Mar Shimun XXII Paulos as Locum Tenens. In December 1918 he was elevated to the rank of Metropolitan in Baghdad Iraq, by the Patriarch. In 1933, he was made administrator of the Church in Iraq and the Middle East. In 1973 when Mar Eshai Shimun XXIII resigned his position as Catholicos Patriarch of the Assyrian Church of the East, Mar Yosip Khnanisho was vested with responsibilities of administering the Church worldwide. At the same time the Iraqi government issued a Republican decree appointing Mar Yosip Khnanisho as the Supreme Head of all the Assyrians in Iraq.