The origin of London Missionary Society was associated with the evangelical revival in England in the last quarter of the eighteenth century. Every Christian in England considered it his duty to strive hard for the spreading of the gospel both at home and abroad. The enlightened Christians in England also advocated strongly in favour of allowing missionaries to spread the gospel in India. This dream became a reality with the founding of missionary societies. Among these, the London Missionary Society stood in the vanguard; it came into being in 1795 on a nondenominational basis. Its motto was Isaiah 52:7 “How beautiful upon the mountains are the feet of him that bringeth good tidings that publisheth peace; that bringeth good tidings of good; that publisheth salvation; that saith unto Zion, Thy God reigneth!” The fundamental principle of the society was "not to send Presbyterianism, Independency, Episcopacy or any other form of church order and Government; but the Glorious Gospel of the blessed God". The history of the missionary activities of the Protestant church in Travancore commenced with the arrival of William Tobias Ringeltaube, a missionary of the LMS in CE 1806. The LMS started its work first among the Parayas and it soon spread among the Nadars. Once the Nadars were considered an oppressed class in Travancore, who were not satisfied with their position. The attention of the missionaries of the LMS was also turned to the lower sections of the society like Parayas, Pulaya, Ezhavas etc, who suffered from caste tyranny and oppression. They were considered as the “lower orders.” The LMS missionaries took a strong stand against caste distinctions within the churches through education. Their aim was to create “an independent, selfsupporting, self-governing and self-propagating native church. The result was the formation of the South India United Church (S.I.U.C) in 1908. When SIUC was formed in South India, Travancore Mission of the LMS was the most successful among the missions in the whole of India.
After the Indian Independence, On 27th September 1947 the General Assembly of South India United Church, the General council of Church of India, Pakistan, Burma and Ceylon, and South India Provincial Synod of Methodist Church joined together to from the CHURCH OF SOUTH INDIA as the largest united national church in India. The continued growth has been further enriched with the joining of the churches of Basel Mission and the Anglican Diocese of Nandyal. A unique church was born out of the blending of the Episcopal and non - Episcopal traditions as a gift of God to the people of India and as a visible sign of the ecclesiastical unity for the universal church.
The Rt.Rev.A.H.Legg was consecrated on 27-09-1947 and installed as the first Bishop of the South Travancore Diocese on 13-10-1947. The South Travancore Diocese was bifurcated into the Kanyakumari Diocese and the South Kerala Diocese in 1959 and the Rt.Rev.A.H.Legg continued to be the first Bishop of the South Kerala Diocese till be returned to England in 1965. The Rt. Rev.William PaulVachalan was consecrated and installed in the South Kerala Diocese on 2-7-1967. He passed away on 5-11-1972 while in service. The Rt.Rev.Isaiah Jesudason, was consecrated and installed in the South Kerala Diocese in 5th August 1973. He was Deputy Moderator of the Church of South India from 1980-81 and Moderator from 1982-1987. He retired from active service on 14th February 1990 on completion of 65 years of age. The Rt.Rev.Dr.Samuel Amirtham was consecrated and installed as Bishop of the Diocese on 20-05-1990. He was director of the Programme on Theological Education and Director of the Ecumenical Institute, Bossey of the WCC 1980-1990. He retired from active service on 19the August 1997. Most.Rev.Dr.J.W.Gladstone, was consecrated and installed as Bishop on 16-9-1997. He was the principal of KUT seminary, Trivandrum and the president of the Senate of Serapore, Culcutta. He is selected as the Moderator of the C.S.I. Synod in 2008. He retired from active service on 25th December 2010 on completion of 65 years of age. The Rt.Rev. A.Dharmaraj Rasalam was consecrated and installed as Bishop on 23.7.2011.