The young Gregory was saved from the extermination of Anak's family and was raised as a Christian in Caesarea of Cappadocia, then part of the Roman Empire.

Gregory, the Illuminator, then healed King Tiridates, who the hagiographical sources say had been transfomed into a boar for his sins, and preached Christianity in Armenia.

[6] In the Armenian tradition, the standard version of the life of Gregory the Illuminator derives from the fifth-century hagiographic history attributed to Agathangelos.

[21][e] After being released, Gregory preached the Christian faith in Armenia and erected shrines to the martyrs Gayane and Hripsime in Vagharshapat on a spot indicated to him in a vision.

[16][f] Vagharshapat would later become home to the mother church of Armenian Christianity and, by medieval times, called Ejmiatsin ("descent of the only-begotten") in reference to Gregory's vision.

[6][31] Gregory is also said to have journeyed to Rome with King Tiridates in an embassy to the recently converted Constantine the Great, but scholar Robert W. Thomson views this as fictional.

[22] Additionally, the history of Agathangelos depicts the spread of Christianity of Armenia as having occurred practically entirely within Gregory's lifetime, when, in fact, it was a more gradual process.

[41] James R. Russell argues that both Gregory and Mashtots were visionaries, found a champion for their program in the king, looked to the West, had very strong pro-Hellenic bias, trained the children of pagan priests and assembled their own disciples to spread the faith through learning.

In the calendar of the Armenian Church, the discovery of the relics of St. Gregory is an important feast and is commemorated on the Saturday before the Fourth Sunday after Pentecost.

[46] He is depicted next to John the Baptist, the prophet Elijah, and most likely Thaddeus, James of Nisibis, and the apostle Bartholomew on the east façade of the tenth-century Aghtamar Cathedral in Lake Van.

[51] At the Vank Cathedral in New Julfa, the Armenian district of Isfahan, Iran, Gregory's martyrdom was painted in a European style by the Italian-trained Hovhannes M'rkuz Jułayeci in 1646.

[56] Located in the south tympanum, next to the Fathers of the Church, it shows Gregory standing in bishop robes, blessing with one hand and holding the Book of the Gospels with the other.

Sirarpie Der Nersessian argued that his inclusion in the series of the Church Fathers is explained by the myth of the Arsacid origin of Basil I, likely fabricated by Patriarch Photios I of Constantinople.

[1] One of the sections of Moscow's iconic Saint Basil's Cathedral is named after Gregory the Armenian (Tserkov Grigoriya Armyanskogo).

[64] In the 8th century, the iconoclast decrees in Greece caused a number of religious orders to flee the Byzantine Empire and seek refuge elsewhere.

San Gregorio Armeno in Naples was built in that century over the remains of a Roman temple dedicated to Ceres, by a group of nuns escaping from the Byzantine Empire with the relics of Gregory,[66] including his skull, arms, a femur bone, his staff, the leather straps used in his torture and the manacles that held the saint.

A 5.7 m (19 ft) tall statue of Gregory in the Carrara marble was installed in the north courtyard of St. Peter's Basilica in Vatican City in January 2005.