Born Timothy Richard Ware in 1934 to an Anglican family in Bath, Somerset, England, he was educated at Westminster School in London and Magdalen College, Oxford, where he took a double first in classics as well as reading theology. On 14 April 1958, at the age of 24, he embraced the Orthodox Christian faith. He describes his first contacts with Orthodoxy and the growing attraction of the Orthodox Church in an autobiographical text entitled "My Journey to the Orthodox Church", While still a layman, he spent six months in Canada at a monastery of the Russian Orthodox Church Abroad. Thoroughly conversant in modern Greek, Ware became an Orthodox monk at the Monastery of Saint John the Theologian in Patmos, Greece. He also frequented other major centres of Orthodoxy such as Jerusalem and Mount Athos. In 1966 he was ordained to the priesthood within the Ecumenical Patriarchate and was tonsured as a monk, receiving the name "Kállistos".
Ware is a prolific author and lecturer. He has authored or edited over a dozen books, numerous articles in a wide range of periodicals, essays in books on many subjects, as well as providing prefaces, forwards or introductions to many other books. He is perhaps best known as the author of the book The Orthodox Church, published when he was a layman in 1963 and subsequently revised several times. In 1979 he produced a companion volume, The Orthodox Way. He has collaborated in the translation and publication of major Orthodox ascetic and liturgical texts. Together with G. E. H. Palmer and Philip Sherrard, he translated the Philokalia ; and with Mother Mary he produced the Lenten Triodion and Festal Menaion. St Vladimir's Seminary Press published a Festschrift in his honour in 2003: Abba, The Tradition of Orthodoxy in the West, Festschrift for Bishop Kallistos of Diokleia, eds. John Behr, Andrew Louth, Dimitri Conomos.
Books
The Orthodox Church.
Eustratios Argenti: A Study of the Greek Church under Turkish Rule ).
The Festal Menaion ).
, Anglican–Orthodox Dialogue: The Moscow Statement Agreed by the Anglican–Orthodox Joint Doctrinal Commission 1976 ).
The Lenten Triodion .
The Philokalia: The Complete Text.
Communion and Intercommunion: A Study of Communion and Intercommunion Based on the Theology and Practice of the Orthodox Church.
The Power of the Name - The Jesus Prayer in Orthodox Spirituality.
Praying with Orthodox Tradition.
How Are We Saved?: The Understanding of Salvation in the Orthodox Tradition.
"Review of Panagiotis N. Trembelas, Dogmatique de l’Église orthodoxe,” Eastern Churches Review 3, 4, 477–480.
"God Hidden and Revealed: The Apophatic Way and the Essence-Energies Distinction", Eastern Churches Review 7.
"The Debate about Palamism", Eastern Churches Review 9.
"Wolves and Monks: Life on the Holy Mountain Today", Sobornost 5, 2.
"Athos after Ten Years: The Good News and the Bad", Sobornost 15, 1.
"Through Creation to the Creator", Third Marco Pallis Memorial Lecture, Ecotheology, 2 .
"Dare We Hope for the Salvation of All?” Theology Digest, 45.4. Reprinted in The Inner Kingdom.
"Man, Woman and the Priesthood of Christ", in Thomas Hopko, ed., Women and the Priesthood.
"God Immanent yet Transcendent: The Divine Energies according to Saint Gregory Palamas" in Philip Clayton and Arthur Peacocke, eds., In Whom We Live and Move and Have Our Being: Panentheistic Reflections on God's Presence in a Scientific World .
"Sobornost and Eucharistic Ecclesiology: Aleksei Khomiakov and His Successors", International Journal for the Study of the Christian Church 11, 2-3.
"Orthodox Theology Today: Trends and Tasks", International Journal for the Study of the Christian Church 12, 2.