Although Mithridates I was a Median prince, little is known on his lineage and his life.
In or before 67 BC, Mithridates I married an unnamed Armenian princess from the Artaxiad dynasty who was a daughter of the Armenian king Tigranes the Great and, possibly, his wife, Cleopatra of Pontus.
Mithridates I is mentioned by Cassius Dio in the last campaign against the Roman general Lucullus in 67 BC.
[3] He was supporting Tigranes, when his father-in-law went to war against the Romans to invade Cappadocia in 67 BC.
[6] According to modern genealogies, Mithridates I and his Armenian wife are presented in being the parents of a child, a son called Ariobarzanes I[7] which can explain the claims of Mithridates I's descendants to the Armenian kingship in opposition to the lasting ruling monarchs of the Artaxiad dynasty.