Born on November 23, 1961, in the city of Perm.

In 1979, he graduated from secondary school No. 72 in Perm.

In 1979, he entered the Perm Polytechnic Institute.

In 1981, due to a change of residence, he transferred to the Vladimir Polytechnic Institute, which he graduated from in 1984 with a degree in "Industrial and Civil Construction."

From 1984 to 1985, he served in the Soviet Armed Forces in the territory of the GDR.

From 1986 to 1989, he served as an altar server in the Holy Protection Church in the city of Alma-Ata.

On March 26, 1989, he was ordained a deacon (celibate) by Bishop Eusebius of Alma-Ata and Kazakhstan (now Metropolitan of Pskov and Porkhov).

On April 7, 1989, he was ordained a presbyter by Bishop Eusebius and appointed a cleric of the Church of the Archangel Michael in the city of Kokshetau.

On November 18, 1989, he was appointed a cleric of the Cathedral of the Archangel Michael in the city of Karaganda.

On February 1, 1991, he was appointed a cleric of the Holy Nicholas Cathedral in the city of Alma-Ata.

Since March 16, 1993, he has been serving as the rector of the Church of the Nativity of Christ in the village of Akbulak in the Almaty region (now the Church of Christ the Savior in the city of Alma-Aty).

From 1995 to 1997, he studied at the Alma-Ata Theological School.

In 1998, he entered the correspondence department of the Moscow Theological Seminary, which he graduated from in 2003.

In 2009, he graduated from the Moscow Theological Academy.

By the decision of the Holy Synod on December 24, 2010 (Journal No. 121), he was elected Bishop of Karaganda and Shahtinsk.

On January 4, 2011, he was tonsured a monk with the name Sebastian in honor of Venerable Confessor Sebastian, Elder of Karaganda, by Metropolitan Alexander of Astana and Kazakhstan.

On January 6, 2011, he was elevated to the rank of archimandrite by Metropolitan Alexander of Astana and Kazakhstan.

On February 18, 2011, at the Patriarchal residence in Chisty Lane, His Holiness Patriarch Kirill of Moscow and All Rus' led the nomination ceremony of Archimandrite Sebastian (Osokin) as Bishop of Karaganda and Shahtinsk.

On February 20, 2011, on the Sunday of the Prodigal Son, during the Divine Liturgy at the Cathedral of Christ the Savior, His Holiness Patriarch Kirill led the consecration of Archimandrite Sebastian (Osokin) as Bishop of Karaganda and Shahtinsk.

On March 25, 2011, at the Synod meeting of the Metropolitan District of the Russian Orthodox Church in the Republic of Kazakhstan, he was elected Chairman of the Commission of the Metropolitan District for Church Construction and Legal Issues.

On May 6, 2022, during the Liturgy at the Cathedral of Christ the Savior in Moscow, he was elevated to the rank of archbishop by His Holiness Patriarch Kirill.

Church Awards:

• 2011 - Order of Saint Alexius, Metropolitan of Moscow, III degree
• 2011 - Order of "Algys" ("Gratitude")
• 2012 - Medal for the "140th Anniversary of the Establishment of the Turkestan Diocese"
• 2013 - Medal for the 10th Anniversary of the Establishment of the Kazakhstan Metropolitan District
• 2014 - Order of Venerable Sebastian, Confessor of Karaganda
• 2015 - Medal for the 1000th Anniversary of the Repose of Equal-to-the-Apostles Great Prince Vladimir
• 2016 - Medal of Venerable Sebastian, Confessor of Karaganda
• 2016 - Order of Venerable Seraphim of Sarov, III degree
• 2016 - Order of Saint Nicholas, Confessor of Alma-Ata
• 2017 - Medal for the 145th Anniversary of the Establishment of the Turkestan Diocese