The Mar Thoma Church is that section of the non-Roman St. Thomas Christians which has undertaken a degree of liturgical and doctrinal reform under the influence of Church of England missionaries in the 19th cent.

The arrival of British administrators and churchmen in early 19th-cent. Kerala coincided with a desire for improved training for clergy. With the encouragement of the British Resident, Colonel Munro, a College was founded at Kottayam under Indian auspices, though it was soon dominated by missionaries of the Anglican Church Missionary Society who arrived in 1816. Under their influence Palakunnathu Abraham, a Malpan from Maramon, agitated for the removal of some liturgical and cultural practices. Abraham was simultaneously genuinely committed to W.-Syr. identity, including the use of Serṭo script, which rapidly replaced E.-Syr. while he was teaching at the College.

Various factions in the community appealed to the Syr. Orth. Patr. at Dayr al-Zaʿfarān, who, in 1842, consecrated a nephew of Abraham Malpan as Mathews Mar Athanasios. His pursuit of reform was inconsistent. He continued as Malankara Metropolitan until his death in 1877, though in the preceding year Patr. Peṭros III had divided Kerala into seven Dioceses for those who wished to live under his jurisdiction. After a decade of litigation, a Court ruling in 1889 declared that Toma Mar Athanasios (successor to Mathews Mar Athanasios) was not Malankara Metropolitan as he had not been consecrated by a patr. of Antioch. The ‘Reformers’ were required to leave the ancient Churches and erect new buildings. They took the name ‘Mar Thoma Syrian Church’.

There was a crisis in 1893 when Toma Mar Athanasios died without having consecrated a successor. Recourse was had to the Malabar Independent Syrian Church, whose bishops travelled to Kottayam in the face of many threats and consecrated a son of Abraham Malpan with the title Titus Mar Thoma. Since then, Thozhiyur bishops have actively participated at every Mar Thoma consecration, thus enabling that Church to remain sacramentally connected to its Oriental Orthodox heritage. On five occasions in the 20th cent. Mar Thoma Metropolitans have consecrated bishops for Thozhiyur.

The ‘agenda’ of the reform was very much determined by the issues which had dominated the English Reformation in the 16th cent.: prayer and the departed, the invocation of saints, eucharistic Presence. The first two were deleted from liturgical practice. With regard to the third, the Mar Thoma anaphoral epiclesis still prays that the Holy Spirit will ‘sanctify this Bread that it may be the Body of our Lord Jesus Christ’ (with a parallel petition over the Cup), though prayer addressed to the Sacramental Christ is omitted. Phrases which Anglican influence suggested were capable of a ‘monophysite’ interpretation were also amended. Only the Councils of Nicaea, Constantinople, and Ephesus are commemorated in the Qurbānā.

The form of the Church’s worship remains unmistakably Syr. Orth. The vestments, church furnishings, chanting, use of incense, and the general dynamics of worship mark it as a Church in the Oriental Orthodox tradition. Its bishops are celibates, distinguished by the monastic schema. They are buried seated in their robes. Beards are optional for priests, but are worn by many (all bishops have them). The white cassock is universal. Most worship is now in Malayalam, though some Syriac formulae remain in use. English and other languages are increasingly used outside India.

The Church has always had a strong commitment to fostering the spiritual life of its members. In the 1880s it inaugurated the world-famous Maramon Convention. Domestic prayer and Bible reading are encouraged. Ashrams and, more recently, a celibate order of priests have been instituted. The Church has several evangelistic missions throughout India, but has not yet applied its evangelistic zeal to any great extent in the Diaspora. There is a long tradition of close relations with the Church of South India and the Church of North India, though the Mar Thoma Church has said that it does not wish to abandon its eastern heritage by uniting with the two western-derived Churches. The Church is actively involved in the World Council of Churches and other ecumenical bodies.

Theological training remains Western in form. Whereas the Malabar Catholic Church has engaged in an active debate about freeing itself from colonially-imposed theological method and rediscovering its Eastern roots, the Mar Thoma Church has not yet ventured upon that process.

The Church today has approximately 1 million members worldwide, under the oversight of ten bishops. The bishops constitute the episcopal synod, presided over by the most senior, who is Metropolitan. The supreme governing body is the Sabha Mandalam, which has over a thousand clergy and lay representatives from all the congregations worldwide, and meets annually.