A native of Chicago born to first-generation Greek-Americans, Merope (nee Kossivas) and the late Christ J. Kantzavelos, Bishop Demetrios of Mokissos grew up as an active participant in the life of the city's historic Assumption Greek Orthodox Community.  He went on to attend Hellenic College and Holy Cross School of Theology in Brookline, Massachusetts, where he obtained his graduate divinity degree “with high distinction” in 1987.  Following graduation, he pursued post-graduate doctoral work in the philosophy program of Chicago's Loyola University, concentrating in the area of metaphysics.   

Having received monastic tonsure, Bishop Demetrios was ordained to the Diaconate October of 1989.  In 1992, he was ordained to the priesthood, and in 1995 elevated to the rank of Archimandrite, all by the hand of Metropolitan Iakovos of Chicago.  Since then, he has served as assistant and deacon to the bishop, as associate pastor of Annunciation Cathedral of Chicago, and presently serves as Chancellor of the Metropolis of Chicago.  

Named as “one of the twelve people to watch” by The Chicago Sun-Times (January 5, 2003), Bishop Demetrios has worked extensively to build bridges of understanding and improve relationships between Chicago’s Greek Orthodox Community with other local Orthodox bodies, as well as other Christian and non-Christian groups. His ecumenical and interfaith commitments are numerous, coalescing around areas of social justice and advocacy.  To this end, in February of 2003, he co-founded a local initiative to improve relations between the Turkish and Greek communities in Chicago, culminating in his being named the recipient of the 2010 “FethullahGulen Award” from the Niagara Foundation, a Turkish/Muslim-American group in Chicago, inspired by FethullahGulen, a leading Turkish Muslim, advancing interfaith and intercultural dialogue.

Bishop Demetrios is the immediate past President (2008-2009) of the Council of Religious Leaders of Metropolitan Chicago.  The Council is composed of chief leaders of the Greater Chicago faith Communities and embraces a broad diversity of theological and religious traditions. It is a microcosm of American religion as it exists in the American heartland.

He is a current representative of the Greek Orthodox Archdiocese of America to the National Council of Churches of Christ (NCCCUSA) and served as the chairperson of several of its committees over the past eight (8) years.

In 1992, Bishop Demetrios established the Bishop's Task Force on AIDS, the first formal Orthodox Christian response to this pandemic in the western hemisphere.  As this ministry received widespread recognition, its founder-coordinator Archimandrite Demetrios was named Outstanding Community Leader by the Cook County Board of Commissioners in 1995, and received the Jim Noone Award for Religious Leadership from the AIDS Pastoral Care Network in 1997.  The Task Force has since become a resource for the entire Greek Orthodox Archdiocese of America.  From 2001 until 2004, Bishop Demetrios also served as board member of Chicago’s Alexian Brothers’ Bonaventure House, a premiere residential care facility for people living with HIV/AIDS.  In August of 2005, he was honored with the Alexian Brothers AIDS Ministry 2005 President’s Award.

With an unyielding commitment to the sanctity of life, Bishop Demetrios works for justice and humanity in the prison system.  He has served as a board member and past two-term President (2003-2005) of the Illinois Coalition to Abolish the Death Penalty and received the coalition’s Cunningham-Carey Award in 2007.  He has spoken and written extensively in support of abolition of the death penalty and has advocated extensively for individual death row inmates. Having met with the Illinois Governor on several occasions on the subject of Capital Punishment, Bishop Demetrios was recognized for his advocacy as an invited guest at the ceremony where Illinois Governor Pat Quinn signed legislation abolishing the death penalty in 2011.

For all these and related activities, in 2008 he was appointed as a member of the Illinois State Advisory Committee of the United States Commission on Civil Rights. In 2011, Bishop Demetrios was honored to be re-appointed for a second term on the Committee.

Bishop Demetrios has also taken a leadership role in numerous Hellenic organizations and cultural events.  In all of these, he has worked to instill a spirit of cooperation by all groups from the intertwined values of Christian Orthodoxy and “ecumenical Hellenism.” He is a regular contributor of editorials in local and national media outlets for issues concerning the Greek Orthodox Faith and Hellenic culture.  

Bishop Demetrios has also contributed to numerous publications including, but not limited to: Echoes From Calvary: Meditations on Franz Joseph Haydn's Seven Last Words of The Christ (Rowman& Littlefield Publishers, Inc, 2005), edited by Richard Young; and, The Revolution: A Field Manual for Changing Your World (Relevant Books, 2006), edited by Heather Zydek.

On October 30, 2006, Archimandrite DemetriosKantzavelos was elected unanimously by the Holy and Sacred Synod of the Ecumenical Patriarchate of Constantinople as Bishop of Mokissos, to serve as an auxiliary bishop of the Holy Archdiocese of America.   He was assigned to serve the needs of the Holy Metropolis of Chicago at the direction of its hierarch, His Eminence Metropolitan Iakovos.  His episcopal ordination took place on December 9, 2006, at his home parish of the Assumption Church, in Chicago, Illinois, by the hand of His Eminence Archbishop Demetrios of America, with Metropolitan Iakovos of Chicago, along with other revered Hierarchs of the Greek Orthodox Archdiocese of America and other Orthodox Christian jurisdictions.

His Grace Bishop Demetrios of Mokissos continues to serve the Holy Metropolis of Chicago as Chancellor.