According to Euthymius I's hagiography, the Vita Euthymii, he helped Leo survive his imprisonment in 883–886, while the young prince constantly requested his advice, forcing him to stay in Constantinople rather than his monastery.

[2] Euthymius I first incurred Leo VI's displeasure when he supported his first wife, Theophano Martinakia, and dissuaded her from seeking a divorce due to the emperor's neglect and his continued cohabitation with his long-time mistress Zoe Zaoutzaina.

[2][9] After Theophano's death, Euthymius I opposed Leo VI's second marriage to Zoe Zaoutzaina due to her ill repute, which earned him a two-year confinement in the monastery of St. Diomedes.

[2][10] Following Zoe's death after giving birth to a daughter, Anna, Leo pursued a — normally un-canonical — third marriage, to Eudokia Baïana, in hopes of having a male heir.

The Vita asserts that following the death of Zoe and her father, as well as the discovery of a conspiracy by their relatives, Leo VI had repented of his treatment of Euthymius I and asked for his forgiveness.

During one of the visits, Euthymius prophesied Eudokia's death and later refused to attend her funeral, retiring with six followers from Constantinople to the suburb of "ta Agathou", a property of his monastery.

The fact that the child's mother was the emperor's mistress caused trouble with leading Church officials, and Leo VI was forced to promise to separate from Zoe as a precondition for the infant's ceremonial baptism by Patriarch Nicholas I in the Hagia Sophia.

[1][13] The Vita explains Nicholas I's stance and his final deposition by his implication in the abortive plot of general Andronikos Doukas, but other sources are silent as to the exact background of the affair.

Its author is unknown, but, in the words of Shaun Tougher, "he had an insider's perspective on court affairs during [Leo VI's] reign", and is consequently one of the "richest sources for the period from the death of Basil I to the early years of Constantine VII" (Alexander Kazhdan).

[1][16][17] The single surviving manuscript was kept in Berlin and vanished during World War II, but the Vita exists in several critical editions:[18] Euthymius I's own writings are few and relatively insignificant, comprising sermons on the conception of Saint Anne and a homily on the Virgin Mary.