Metropolitan Theodosius was born in Canonsburg, PA in 1933 to immigrant parents from Galicia, in what is today the southeastern corner of Poland. After completing undergraduate studies at Washington and Jefferson College, Washington, PA, he enrolled in Saint Vladimir's Orthodox Theological Seminary, New York, from which he received a Master of Divinity degree in 1960. He spent the next year pursuing additional studies at the Ecumenical Institute in Bossey, Switzerland, touring the Holy Land, and visiting Orthodox Christian centers throughout Europe and the Middle East.