He was born Dikran Israelian in New Julfa, Persia. He was ordained deacon in December 1921 and celibate priest (taking the name Guregh) in July 1923. In July 1944 the Brotherhood of St James elected him as locum tenens of the Patriarchate of Jerusalem after the death of Patriarch Mesrob. He was elected Patriarch in October 1944. He was finally consecrated bishop in Echmiadzin on 1 July 1945, becoming an archbishop on 16 July 1945. He was installed as Patriarch in the Cathedral of St James on 6 December 1945 after the British King George VI had given the necessary assent.
Upon his death in 1949, the position of Patriarch of Jerusalem remained vacant for more than a decade, i.e. from 1949 to 1957 and from 1958 to 1960, with a very brief period when Tiran Nersoyan was elected as patriarch of Jerusalem (1957–1958), but was never consecrated.
Only in 1960 was a new Armenian Patriarch of Jerusalem officially elected, namely Patriarch Yeghishe Derderian. Earlier since 1949, Derderian was serving as deputy patriarch.