Archbishop Hagopian was born in Syria on June 20, 1946. At a young age, he and his family relocated to Lebanon, where he received his education at Torkomian School and in 1961 entered the Seminary at the Catholicosate of the Holy See of Cilicia in Antelias. In 1965 he is ordained a deacon by then Bishop Karekin Sarkisian, who later became the Catholicos of the Holy See of Cilicia and the Catholicos of All Armenians.

In 1968, Deacon Hagopian was ordained a celibate priest and later in 1971 he received the title of Very Reverend -Vartabed.

Very Rev. Fr. Khajag Hagopian was elected the Locum Tenens of Jezireh, Northern Syria Prelacy. After serving in that capacity for eight years, he returned to Lebanon where he resumed his academic studies at the Middle East Theological institute. In 1981, at the invitation of Arch. Mesrob Ashjian, then the Prelate of Eastern US and Canada, Very Rev. Fr. Hagopian relocated to New York where he served as special assistant to the Prelate.

In 1983, he became the first parish priest of the newly established St. Mary Church in Toronto. In 1985 he was ordained a Right Reverend by Arch. Ashjian. In 1994, Bishop Hagopian served as the parish priest of the Holy Martyrs Armenian Church in Encino only to return to New York in 1995, where he led the congregation at the St. Gregory the Illuminator Church.

In June of 1997, His Holiness Aram I, Catholicos of the Holy See of Cilicia ordained him Bishop, and in 2002 the Catholicos appointed Bishop Hagopian as the Locum Tenens of the Canadian Prelacy.

On May 28, 2003 he was elevated to Archbishop by an Encyclical from His Holiness Aram in February 2004 he became the Prelate of the Armenian Prelacy of Canada.

On May 11, 2006 he was reelected as Prelate of Canada for another term, during the Canadian Armenian National Assembly Representatives meeting in St. Catherines.

On May 8, 2010, Archbishop Hagopian was reelected for the third time as Prelate of Canada at the Canadian Armenian National Assembly Representatives meeting in Toronto.