Saint Theodoritus left home and went to the Solovki Monastery when he was only thirteen years old. The following year he was tonsured and placed under obedience to the wise Father Zosimas. For the next fifteen years he grew in wisdom and virtue, then was ordained a deacon by the Archbishop of Novgorod.
Saint Theodoritus spent one more year with his Elder, then asked for permission to visit other monasteries. At each place he spoke with experienced ascetics, deriving much spiritual profit from their conversation. After two years at the White Lake Monastery, Saint Theodoritus lived alone in the forest around the monastery. During his four years in the forest, he came into contact with other ascetics, from whom he learned many useful things.
Father Zosimas at Solovki, sensing that he would die soon, wrote to Saint Theodoritus asking him to return to him. He served his Elder for about a year, taking care of him during his final illness.
Saint Theodoritus then traveled to the mouth of the Kola River and undertook missionary labors among the Lapps with the Elder Metrophanes. The Lapps worshiped idols and did not live in towns or cities. The monks learned their language so they could teach them about Christ, and also translated prayers for them.
Saint Theodoritus labored among the Lapps for twenty years. He was ordained to the holy priesthood in Novgorod, and later returned to the Lapps and established a monastery. He then spent two years in the Novgorod area as igumen of a monastery. Later, he was raised to the rank of archimandrite and became the igumen of the Savior-Saint Euthymius Monastery at Suzdal for five years.
In 1554 Saint Theodoritus was slandered and confined for two years at the White Lake Monastery. Upon his release, he went to live in a monastery at Yaroslav. Tsar Ivan the Terrible sent him to Constantinople in 1558 to discuss his coronation with the Patriarch.
Saint Theodoritus returned to Russia with the Patriarch’s reply, and the Tsar gave him twenty-five silver coins and a sable coat. Not wishing to acquire material possessions, the saint sold the coat and gave the money away to the poor.
Searching for peace, he went to the monastery at Priluki in Vologda. From there, Saint Theodoritus made two visits to the Lapps whom he had converted. He departed to the Lord on August 17, 1571 at the Solovki Monastery where he had been tonsured.