His Eminence Bishop Sahag Yemishyan was born in 1983 in Armenia and completed his secondary education in the city of Lussarat. In 1997, he was admitted to the Theological School of the Patriarchate of the Great House of Cilicia in the suburb of Bikfaya in Beirut.

After completing the five-year cycle of studies, he was ordained a subdeacon on May 5, 2002 by the late Archbishop Vartan Demirjian. Later, at the end of the second period of the School, in May 2004, he was ordained a deacon by Archbishop Kegam Khatcherian.

On May 14, 2006, after completing the four-year cycle of the Theological School, he was ordained a hierodeacon by Archbishop Varuzhan Herkelian. In December 2010, after defending his doctoral thesis, he received the rank of Archimandrite from the hands of Archbishop Komitas Ohanian.

On May 29, 2016, in the United States of America, he received the rank of High Archimandrite from the hands of Archbishop Osakan Tsologian.

In 2006-2010, he assumed various duties within the Holy Monastery of the Patriarchate, such as deputy director and then director of the Archives, supervisor of the Youth Office and advisor to the Student Union of the Ecclesiastical School. He has taught at the Theological School for candidate hieromonks, as well as at the school of elders of the Patriarchate.

In 2009, he attended English language courses at the American Language Center in Lebanon.

In 2010, he was appointed pastor of the Armenian Community of Thessaloniki. In 2011, he attended Modern Greek language courses at the Aristotle University of Thessaloniki.

In 2013, he left for the United States where he was appointed pastor of the Holy Trinity Church in Worcester.

In 2018, he received a Master of Theology and Pastoral Care (M.A.T.M.) from Boston College.

Since 2021, he has been continuing his higher studies at Fordham University, pursuing a Ph.D. in Administration and Leadership.

In 2019, he was appointed pastor of the Holy Church of Saints Vartanants in New Jersey. In the same year, he was also appointed Alternate Metropolitan of the Armenian Community of the Eastern United States.

In July 2024, he was elected Metropolitan of the Orthodox Armenians of Greece.

On February 23, 2025, he was ordained Bishop of the Catholicosate of the Great House of Cilicia in Antilias, Lebanon.